Add @Override to toString

src/Aufgabe1Test.java

@@ -1,17 +1,19 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 public class Aufgabe1Test {
 
-    public static void main(String[] args) {
-        //test classes Body and Vector3
-
+    @Test
+    public void testEP2() {
         // create two bodies
-        Body sun = new Body(1.989e30,new Vector3(0,0,0),new Vector3(0,0,0));
-        Body earth = new Body(5.972e24,new Vector3(-1.394555e11,5.103346e10,0),new Vector3(-10308.53,-28169.38,0));
+        Body sun = new Body(SolSystem.SUN);
+        Body earth = new Body(SolSystem.EARTH);
 
-        testValue(earth.distanceTo(sun), 1.4850000175024106E11);
-        testValue(sun.distanceTo(earth), 1.4850000175024106E11);
+        assertEquals(1.4850000175024106E11, earth.distanceTo(sun));
+        assertEquals(1.4850000175024106E11, sun.distanceTo(earth));
 
-        for(int i = 0; i < 3600*24; i++) {
+        for (int i = 0; i < 3600 * 24; i++) {
             Vector3 f1 = earth.gravitationalForce(sun);
             Vector3 f2 = sun.gravitationalForce(earth);
 
@@ -20,36 +22,9 @@ public class Aufgabe1Test {
         }
 
         // a dummy body to check the correct position after 24h of movement
-        Body targetPositionEarth = new Body(1, new Vector3(-1.403250141841815E11,
-                4.859202658875631E10, 0.0), new Vector3(0,0,0));
+        Body targetPositionEarth = new Body(1, new Vector3(-1.403250141841815E11, 4.859202658875631E10, 0.0), new Vector3(0, 0, 0));
 
         // check distance to target position (should be zero)
-        testValue(earth.distanceTo(targetPositionEarth), 0);
-    }
-
-    public static void testComparison(Object first, Object second, boolean expected) {
-        boolean real = first == second;
-
-        if (real == expected) {
-            System.out.println("Successful comparison");
-        } else {
-            System.out.println("Comparison NOT successful! Expected value: " + expected + " / Given value: " + real);
-        }
-    }
-
-    public static void testValue(Object given, Object expected) {
-        if (given == expected) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
-    }
-
-    public static void testValue(double given, double expected) {
-        if (given < expected + (expected+1)/1e12 && given > expected - (expected+1)/1e12) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
+        assertEquals(0, earth.distanceTo(targetPositionEarth));
     }
 }

src/Aufgabe2Test.java

@@ -1,80 +1,51 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
 public class Aufgabe2Test {
 
-    public static void main(String[] args) {
-
-        //test classes BodyQueue and BodyForceMap
-
+    @Test
+    public void testEP2() {
         // create three bodies
-        Body sun = new Body(1.989e30,new Vector3(0,0,0),new Vector3(0,0,0));
-        Body earth = new Body(5.972e24,new Vector3(-1.394555e11,5.103346e10,0),new Vector3(-10308.53,-28169.38,0));
-        Body mercury = new Body(3.301e23,new Vector3(-5.439054e10,9.394878e9,0),new Vector3(-17117.83,-46297.48,-1925.57));
-
+        Body sun = new Body(SolSystem.SUN);
+        Body earth = new Body(SolSystem.EARTH);
+        Body mercury = new Body(SolSystem.MERCURY);
 
         // check basic functions of 'BodyQueue'
-        System.out.println("Test1:");
-
         BodyQueue bq = new BodyQueue(2);
         bq.add(mercury);
         bq.add(sun);
         bq.add(earth);
-        testValue(bq.size(), 3);
+        assertEquals(3, bq.size());
 
-        testValue(bq.poll(), mercury);
-        testValue(bq.poll(), sun);
-        testValue(bq.poll(), earth);
+        assertEquals(mercury, bq.poll());
+        assertEquals(sun, bq.poll());
+        assertEquals(earth, bq.poll());
 
-        testValue(bq.size(), 0);
+        assertEquals(0, bq.size());
 
         bq.add(mercury);
         bq.add(sun);
-        testValue(bq.size(), 2);
+        assertEquals(2, bq.size());
 
         // check constructor of 'BodyQueue'
         BodyQueue bqCopy = new BodyQueue(bq);
-        testComparison(bq, bqCopy, false);
-        testComparison(bq.poll(), bqCopy.poll(), true);
+        assertNotEquals(bq, bqCopy);
+        assertEquals(bqCopy.poll(), bq.poll());
         bq.add(earth);
-        testValue(bq.size(), 2);
-        testValue(bqCopy.size(), 1);
+        assertEquals(2, bq.size());
+        assertEquals(1, bqCopy.size());
 
         // check basic functions of 'BodyForceMap'
-        System.out.println("Test2:");
         BodyForceMap bfm = new BodyForceMap(5);
         bfm.put(earth, earth.gravitationalForce(sun));
         bfm.put(sun, sun.gravitationalForce(earth));
 
-        testValue(bfm.get(earth).distanceTo(earth.gravitationalForce(sun)),0);
-        testValue(bfm.get(sun).distanceTo(sun.gravitationalForce(earth)),0);
+        assertEquals(0, bfm.get(earth).distanceTo(earth.gravitationalForce(sun)));
+        assertEquals(0, bfm.get(sun).distanceTo(sun.gravitationalForce(earth)));
 
-        bfm.put(earth, new Vector3(0,0,0));
-        testValue(bfm.get(earth).distanceTo(new Vector3(0,0,0)), 0);
-        testValue(bfm.get(mercury),null);
-
-    }
-
-    public static void testComparison(Object first, Object second, boolean expected) {
-        boolean real = first == second;
-
-        if (real == expected) {
-            System.out.println("Successful comparison");
-        } else {
-            System.out.println("Comparison NOT successful! Expected value: " + expected + " / Given value: " + real);
-        }
-    }
-
-    public static void testValue(Object given, Object expected) {
-        if (given == expected) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
-    }
-
-    public static void testValue(double given, double expected) {
-        if (given < expected + (expected+1)/1e12 && given > expected - (expected+1)/1e12) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
+        bfm.put(earth, new Vector3(0, 0, 0));
+        assertEquals(0, bfm.get(earth).distanceTo(new Vector3(0, 0, 0)));
+        assertNull(bfm.get(mercury));
     }
 }

src/Aufgabe3Test.java

@@ -1,73 +1,67 @@
-import java.util.Objects;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 public class Aufgabe3Test {
 
-    public static void main(String[] args) {
-
-        //test classes BodyLinkedList and BodyForceTreeMap
-
+    @Test
+    public void testEP2() {
         // create five bodies
-        Body sun = new Body(1.989e30, new Vector3(0, 0, 0), new Vector3(0, 0, 0));
-        Body earth = new Body(5.972e24, new Vector3(-1.394555e11, 5.103346e10, 0), new Vector3(-10308.53, -28169.38, 0));
-        Body mercury = new Body(3.301e23, new Vector3(-5.439054e10, 9.394878e9, 0), new Vector3(-17117.83, -46297.48, -1925.57));
-        Body venus = new Body(4.86747e24, new Vector3(-1.707667e10, 1.066132e11, 2.450232e9), new Vector3(-34446.02, -5567.47, 2181.10));
-        Body mars = new Body(6.41712e23, new Vector3(-1.010178e11, -2.043939e11, -1.591727E9), new Vector3(20651.98, -10186.67, -2302.79));
+        Body sun = new Body(SolSystem.SUN);
+        Body earth = new Body(SolSystem.EARTH);
+        Body mercury = new Body(SolSystem.MERCURY);
+        Body venus = new Body(SolSystem.VENUS);
+        Body mars = new Body(SolSystem.MARS);
 
         // check basic functions of 'BodyLinkedList'
-        System.out.println("Test1:");
-
         BodyLinkedList bl = new BodyLinkedList();
 
         bl.addLast(mercury);
         bl.addLast(sun);
         bl.addLast(earth);
-        testValue(bl.size(), 3);
+        assertEquals(3, bl.size());
 
-        testValue(bl.getFirst(), mercury);
-        testValue(bl.getLast(), earth);
+        assertEquals(mercury, bl.getFirst());
+        assertEquals(earth, bl.getLast());
 
-        testValue(bl.get(0), mercury);
-        testValue(bl.get(1), sun);
-        testValue(bl.get(2), earth);
+        assertEquals(mercury, bl.get(0));
+        assertEquals(sun, bl.get(1));
+        assertEquals(earth, bl.get(2));
 
-        System.out.println("Test2:");
-        testValue(bl.indexOf(earth), 2);
-        testValue(bl.indexOf(sun), 1);
-        testValue(bl.indexOf(mercury), 0);
+        assertEquals(2, bl.indexOf(earth));
+        assertEquals(1, bl.indexOf(sun));
+        assertEquals(0, bl.indexOf(mercury));
 
-        System.out.println("Test3:");
-        testValue(bl.pollFirst(), mercury);
-        testValue(bl.pollLast(), earth);
-        testValue(bl.pollFirst(), sun);
+        assertEquals(mercury, bl.pollFirst());
+        assertEquals(earth, bl.pollLast());
+        assertEquals(sun, bl.pollFirst());
 
-        testValue(bl.size(), 0);
-        testValue(bl.getFirst(), null);
+        assertEquals(0, bl.size());
+        assertNull(bl.getFirst());
 
-        System.out.println("Test4:");
         bl.addFirst(earth);
         bl.addFirst(venus);
         bl.addFirst(sun);
         bl.add(1, mercury);
         bl.add(4, mars);
 
-        testValue(bl.size(), 5);
+        assertEquals(5, bl.size());
 
-        testValue(bl.get(0), sun);
-        testValue(bl.get(1), mercury);
-        testValue(bl.get(2), venus);
-        testValue(bl.get(3), earth);
-        testValue(bl.get(4), mars);
+        assertEquals(sun, bl.get(0));
+        assertEquals(mercury, bl.get(1));
+        assertEquals(venus, bl.get(2));
+        assertEquals(earth, bl.get(3));
+        assertEquals(mars, bl.get(4));
 
         // check constructor of 'BodyLinkedList'
         BodyLinkedList blCopy = new BodyLinkedList(bl);
-        testComparison(bl, blCopy, false);
-        testComparison(bl.pollFirst(), blCopy.pollFirst(), true);
+        assertNotEquals(bl, blCopy);
+        assertEquals(blCopy.pollFirst(), bl.pollFirst());
         bl.addFirst(sun);
-        testValue(bl.size(), 5);
-        testValue(blCopy.size(), 4);
+        assertEquals(5, bl.size());
+        assertEquals(4, blCopy.size());
 
         // check basic functions of 'BodyForceTreeMap'
-        System.out.println("Test5:");
         BodyForceTreeMap bfm = new BodyForceTreeMap();
         bfm.put(earth, earth.gravitationalForce(sun));
         bfm.put(sun, sun.gravitationalForce(earth).plus(sun.gravitationalForce(venus)));
@@ -75,38 +69,11 @@ public class Aufgabe3Test {
         bfm.put(mars, mars.gravitationalForce(sun));
         bfm.put(mercury, mercury.gravitationalForce(sun));
 
-        testValue(bfm.get(earth).distanceTo(earth.gravitationalForce(sun)), 0);
-        testValue(bfm.get(sun).distanceTo(sun.gravitationalForce(earth).plus(sun.gravitationalForce(venus))), 0);
+        assertEquals(0, bfm.get(earth).distanceTo(earth.gravitationalForce(sun)));
+        assertEquals(0, bfm.get(sun).distanceTo(sun.gravitationalForce(earth).plus(sun.gravitationalForce(venus))));
 
-        testValue(bfm.put(earth, new Vector3(0, 0, 0)).distanceTo(earth.gravitationalForce(sun)), 0);
-        testValue(bfm.get(earth).distanceTo(new Vector3(0, 0, 0)), 0);
-        testValue(bfm.get(mercury), mercury.gravitationalForce(sun));
-
-    }
-
-    public static void testComparison(Object first, Object second, boolean expected) {
-        boolean real = first == second;
-
-        if (real == expected) {
-            System.out.println("Successful comparison");
-        } else {
-            System.out.println("Comparison NOT successful! Expected value: " + expected + " / Given value: " + real);
-        }
-    }
-
-    public static void testValue(Object given, Object expected) {
-        if (given == expected) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
-    }
-
-    public static void testValue(double given, double expected) {
-        if (given < expected + (expected + 1) / 1e12 && given > expected - (expected + 1) / 1e12) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
+        assertEquals(0, bfm.put(earth, new Vector3(0, 0, 0)).distanceTo(earth.gravitationalForce(sun)));
+        assertEquals(0, bfm.get(mercury).distanceTo(mercury.gravitationalForce(sun)));
+        assertEquals(mercury.gravitationalForce(sun), bfm.get(mercury));
     }
 }

src/Body.java

@@ -4,7 +4,7 @@ import codedraw.CodeDraw;
  * This class represents celestial bodies like stars, planets, asteroids, etc...
  */
 public class Body {
-    private double mass;
+    private final double mass;
     private Vector3 massCenter; // position of the mass center.
     private Vector3 currentMovement;
 
@@ -14,6 +14,12 @@ public class Body {
         this.currentMovement = currentMovement;
     }
 
+    public Body(Body other) {
+        this.mass = other.mass;
+        this.massCenter = new Vector3(other.massCenter);
+        this.currentMovement = new Vector3(other.currentMovement);
+    }
+
     /**
      * Returns the distance between the mass centers of this body and the specified body 'b'.
      */
@@ -70,16 +76,20 @@ public class Body {
         return mass;
     }
 
+    public boolean collidesWith(Body body) {
+        return this.distanceTo(body) < this.radius() + body.radius();
+    }
+
     /**
      * Returns a new body that is formed by the collision of this body and 'b'. The impulse
      * of the returned body is the sum of the impulses of 'this' and 'b'.
      */
-    public Body merge(Body b) {
-        double mass = this.mass + b.mass;
+    public Body merge(Body body) {
+        double totalMass = this.mass + body.mass;
         return new Body(
-                mass,
-                massCenter.times(this.mass).plus(b.massCenter.times(b.mass)).times(1.0 / mass),
-                currentMovement.times(this.mass).plus(b.currentMovement.times(b.mass)).times(1.0 / mass)
+                totalMass,
+                this.massCenter.times(this.mass).plus(body.massCenter.times(body.mass)).times(1.0 / totalMass),
+                this.currentMovement.times(this.mass).plus(body.currentMovement.times(body.mass)).times(1.0 / totalMass)
         );
     }
 
@@ -100,9 +110,10 @@ public class Body {
      * mass, position (mass center) and current movement. Example:
      * "5.972E24 kg, position: [1.48E11,0.0,0.0] m, movement: [0.0,29290.0,0.0] m/s."
      */
+    @Override
     public String toString() {
         return String.format(
-                "%f kg, position: %s m, movement: %s m/s.",
+                "%g kg, position: %s m, movement: %s m/s.",
                 mass, massCenter.toString(), currentMovement.toString()
         );
     }

src/BodyForceTreeMap.java

@@ -1,40 +1,155 @@
-// A map that associates a Body with a Vector3 (typically this is the force exerted on the body).
-// The number of key-value pairs is not limited.
+/**
+ * A map that associates a Body with a Vector3 (typically this is the force exerted on the body).
+ * The number of key-value pairs is not limited.
+ */
 public class BodyForceTreeMap {
+    private int size = 0;
+    private BodyForceTreeMapItem root = null;
 
-    //TODO: declare variables.
-
-    // Adds a new key-value association to this map. If the key already exists in this map,
-    // the value is replaced and the old value is returned. Otherwise 'null' is returned.
-    // Precondition: key != null.
+    /**
+     * Adds a new key-value association to this map. If the key already exists in this map,
+     * the value is replaced and the old value is returned. Otherwise 'null' is returned.
+     * Precondition: key != null.
+     */
     public Vector3 put(Body key, Vector3 value) {
-
-        //TODO: implement method.
+        if (root == null) {
+            root = new BodyForceTreeMapItem(key, value);
+            size++;
             return null;
         }
 
-    // Returns the value associated with the specified key, i.e. the method returns the force vector
-    // associated with the specified key. Returns 'null' if the key is not contained in this map.
-    // Precondition: key != null.
+        BodyForceTreeMapItem item = root;
+        while (item != null) {
+            if (item.key() == key) {
+                Vector3 old = item.value();
+                item.setValue(value);
+                return old;
+            } else if (item.key().mass() > key.mass()) {
+                if (item.left() != null) {
+                    item = item.left();
+                } else {
+                    item.setLeft(new BodyForceTreeMapItem(key, value));
+                    size++;
+                    break;
+                }
+            } else {
+                if (item.right() != null) {
+                    item = item.right();
+                } else{
+                    item.setRight(new BodyForceTreeMapItem(key, value));
+                    size++;
+                    break;
+                }
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Returns the value associated with the specified key, i.e. the method returns the force vector
+     * associated with the specified key. Returns 'null' if the key is not contained in this map.
+     * Precondition: key != null.
+     */
     public Vector3 get(Body key) {
-
-        //TODO: implement method.
+        BodyForceTreeMapItem item = root;
+        while (item != null) {
+            if (item.key() == key) {
+                return item.value();
+            } else if (item.key().mass() > key.mass()) {
+                item = item.left();
+            } else {
+                item = item.right();
+            }
+        }
         return null;
     }
 
-    // Returns 'true' if this map contains a mapping for the specified key.
+    /**
+     * Returns 'true' if this map contains a mapping for the specified key.
+     */
     public boolean containsKey(Body key) {
-
-        //TODO: implement method.
+        BodyForceTreeMapItem item = root;
+        while (item != null) {
+            if (item.key() == key) {
+                return true;
+            } else if (item.key().mass() > key.mass()) {
+                item = item.left();
+            } else {
+                item = item.right();
+            }
+        }
         return false;
     }
 
-    // Returns a readable representation of this map, in which key-value pairs are ordered
-    // descending according to the mass of the bodies.
+    public int size() {
+        return this.size;
+    }
+
+    private String toString(BodyForceTreeMapItem item) {
+        String s = "";
+        if (item == null) {
+            return s;
+        }
+        s += this.toString(item.right());
+        s += String.format("{%s: %s}\n", item.key(), item.value());
+        s += this.toString(item.left());
+        return s;
+    }
+
+    /**
+     * Returns a readable representation of this map, in which key-value pairs are ordered
+     * descending according to the mass of the bodies.
+     */
+    @Override
     public String toString() {
-
-        //TODO: implement method.
-        return null;
-
+        return toString(root);
+    }
+}
+
+class BodyForceTreeMapItem {
+    private final Body key;
+    private Vector3 value;
+    private BodyForceTreeMapItem parent;
+    private BodyForceTreeMapItem left;
+    private BodyForceTreeMapItem right;
+
+    public BodyForceTreeMapItem(Body key, Vector3 value) {
+        this.key = key;
+        this.value = value;
+    }
+
+    public Body key() {
+        return this.key;
+    }
+
+    public void setValue(Vector3 value) {
+        this.value = value;
+    }
+
+    public Vector3 value() {
+        return this.value;
+    }
+
+    public BodyForceTreeMapItem left() {
+        return this.left;
+    }
+
+    public BodyForceTreeMapItem right() {
+        return this.right;
+    }
+
+    public BodyForceTreeMapItem parent() {
+        return this.parent;
+    }
+
+    public void setLeft(BodyForceTreeMapItem left) {
+        this.left = left;
+        if (left != null) left.parent = this;
+    }
+
+    public void setRight(BodyForceTreeMapItem right) {
+        this.right = right;
+        if (right != null) right.parent = this;
     }
 }

src/BodyLinkedList.java

@@ -1,103 +1,261 @@
-// A list of bodies implemented as a linked list.
-// The number of elements of the list is not limited.
-public class BodyLinkedList {
+import java.util.Iterator;
 
-    //TODO: declare variables.
+/**
+ * A list of bodies implemented as a linked list.
+ * The number of elements of the list is not limited.
+ */
+public class BodyLinkedList implements Iterable<Body> {
+    private int size = 0;
+    private BodyLinkedListItem first;
+    private BodyLinkedListItem last;
 
-    // Initializes 'this' as an empty list.
+    /**
+     * Initializes 'this' as an empty list.
+     */
     public BodyLinkedList() {
-
-        //TODO: define constructor.
+        first = null;
+        last = null;
     }
 
-    // Initializes 'this' as an independent copy of the specified list 'list'.
-    // Calling methods of this list will not affect the specified list 'list'
-    // and vice versa.
-    // Precondition: list != null.
+    /**
+     * Initializes 'this' as an independent copy of the specified list 'list'.
+     * Calling methods of this list will not affect the specified list 'list'
+     * and vice versa.
+     * Precondition: list != null.
+     */
     public BodyLinkedList(BodyLinkedList list) {
-
-        //TODO: define constructor.
+        this.size = 0;
+        for (Body b : list) {
+            this.addLast(b);
+        }
     }
 
-    // Inserts the specified element 'body' at the beginning of this list.
+    /**
+     * Inserts the specified element 'body' at the beginning of this list.
+     */
     public void addFirst(Body body) {
-
-        //TODO: implement method.
+        if (first == null) {
+            first = new BodyLinkedListItem(body);
+            last = first;
+        } else {
+            first.setPrev(new BodyLinkedListItem(body));
+            first = first.prev();
+        }
+        size++;
     }
 
-    // Appends the specified element 'body' to the end of this list.
+    /**
+     * Appends the specified element 'body' to the end of this list.
+     */
     public void addLast(Body body) {
-
-        //TODO: implement method.
+        if (last == null) {
+            last = new BodyLinkedListItem(body);
+            first = last;
+        } else {
+            last.setNext(new BodyLinkedListItem(body));
+            last = last.next();
+        }
+        size++;
     }
 
-    // Returns the last element in this list.
-    // Returns 'null' if the list is empty.
+    /**
+     * Returns the last element in this list.
+     * Returns 'null' if the list is empty.
+     */
     public Body getLast() {
-
-        //TODO: implement method.
-        return null;
+        return (last != null) ? last.body() : null;
     }
 
-    // Returns the first element in this list.
-    // Returns 'null' if the list is empty.
+    /**
+     * Returns the first element in this list.
+     * Returns 'null' if the list is empty.
+     */
     public Body getFirst() {
-
-        //TODO: implement method.
-        return null;
+        return (first != null) ? first.body() : null;
     }
 
-    // Retrieves and removes the first element in this list.
-    // Returns 'null' if the list is empty.
+    /**
+     * Retrieves and removes the first element in this list.
+     * Returns 'null' if the list is empty.
+     */
     public Body pollFirst() {
-
-        //TODO: implement method.
+        if (first == null) {
             return null;
         }
+        Body b = first.body();
+        first = first.next();
+        if (first != null) first.setPrev(null);
+        size--;
+        return b;
+    }
 
-    // Retrieves and removes the last element in this list.
-    // Returns 'null' if the list is empty.
+    /**
+     * Retrieves and removes the last element in this list.
+     * Returns 'null' if the list is empty.
+     */
     public Body pollLast() {
-
-        //TODO: implement method.
+        if (last == null) {
             return null;
         }
+        Body b = last.body();
+        last = last.prev();
+        if (last != null) last.setNext(null);
+        size--;
+        return b;
+    }
 
-    // Inserts the specified element 'body' at the specified position in this list.
-    // Precondition: i >= 0 && i <= size().
+    /**
+     * Inserts the specified element 'body' at the specified position in this list.
+     * Precondition: i >= 0 && i <= size().
+     */
     public void add(int i, Body body) {
-
-        //TODO: implement method.
+        if (first == null || i == 0) {
+            addFirst(body);
+            return;
+        } else if (i == size) {
+            addLast(body);
+            return;
         }
 
-    // Returns the element at the specified position in this list.
-    // Precondition: i >= 0 && i < size().
+        BodyLinkedListItem item = first;
+        for (int j = 0; j < i; j++) {
+            item = item.next();
+        }
+
+        item.prev().setNext(new BodyLinkedListItem(body));
+        item.setPrev(item.prev().next());
+        size++;
+    }
+
+    private Body removeItem(BodyLinkedListItem item) {
+        if (item == first) {
+            first = item.next();
+            if (first != null) first.setPrev(null);
+        } else if (item == last) {
+            last = item.prev();
+            if (last != null) last.setNext(null);
+        } else {
+            item.next().setPrev(item.prev());
+        }
+        size--;
+        return item.body();
+    }
+
+    /**
+     * Returns the element at the specified position in this list.
+     * Precondition: i >= 0 && i < size().
+     */
     public Body get(int i) {
-
-        //TODO: implement method.
-        return null;
+        BodyLinkedListItem item;
+        if (i < size / 2) {
+            item = first;
+            for (int j = 0; j < i; j++) {
+                item = item.next();
+            }
+        } else {
+            item = last;
+            for (int j = size - 1; j > i; j--) {
+                item = item.prev();
+            }
+        }
+        return item.body();
     }
 
-    // Returns the index of the first occurrence of the specified element in this list, or -1 if
-    // this list does not contain the element.
+    /**
+     * Returns the index of the first occurrence of the specified element in this list, or -1 if
+     * this list does not contain the element.
+     */
     public int indexOf(Body body) {
-
-        //TODO: implement method.
-        return -2;
-    }
-
-    // Removes all bodies of this list, which are colliding with the specified
-    // body. Returns a list with all the removed bodies.
-    public BodyLinkedList removeCollidingWith(Body body) {
-
-        //TODO: implement method.
-        return null;
-    }
-
-    // Returns the number of bodies in this list.
-    public int size() {
-
-        //TODO: implement method.
+        if (first == null) {
             return -1;
         }
+
+        BodyLinkedListItem item = first;
+        for (int i = 0; i < size; i++) {
+            if (item.body() == body) {
+                return i;
+            }
+            item = item.next();
+        }
+
+        return -1;
+    }
+
+    /**
+     * Removes all bodies of this list, which are colliding with the specified
+     * body. Returns a list with all the removed bodies.
+     */
+    public BodyLinkedList removeCollidingWith(Body body) {
+        BodyLinkedList removed = new BodyLinkedList();
+        for (BodyLinkedListItem item = first; item != null; item = item.next()) {
+            if (body != item.body() && body.collidesWith(item.body())) {
+                removed.addLast(this.removeItem(item));
+            }
+        }
+        return removed;
+    }
+
+    /**
+     * Returns the number of bodies in this list.
+     */
+    public int size() {
+        return size;
+    }
+
+    @Override
+    public Iterator<Body> iterator() {
+        return new Iterator<>() {
+            BodyLinkedListItem ptr = first;
+            boolean yieldedFirst = false;
+
+            @Override
+            public boolean hasNext() {
+                return ptr != null && (!yieldedFirst || ptr.next() != null);
+            }
+
+            @Override
+            public Body next() {
+                if (!yieldedFirst) {
+                    yieldedFirst = true;
+                    return ptr.body();
+                }
+                ptr = ptr.next();
+                return ptr.body();
+            }
+        };
+    }
+}
+
+class BodyLinkedListItem {
+    private final Body body;
+    private BodyLinkedListItem prev;
+    private BodyLinkedListItem next;
+
+    public BodyLinkedListItem(Body body) {
+        this.body = body;
+        this.prev = null;
+        this.next = null;
+    }
+
+    public Body body() {
+        return body;
+    }
+
+    public BodyLinkedListItem prev() {
+        return prev;
+    }
+
+    public void setPrev(BodyLinkedListItem prev) {
+        this.prev = prev;
+        if (prev != null) prev.next = this;
+    }
+
+    public BodyLinkedListItem next() {
+        return next;
+    }
+
+    public void setNext(BodyLinkedListItem next) {
+        this.next = next;
+        if (next != null) next.prev = this;
+    }
 }

src/BodyQueue.java

@@ -27,15 +27,15 @@ public class BodyQueue {
      * Initializes this queue as an independent copy of the specified queue.
      * Calling methods of this queue will not affect the specified queue
      * and vice versa.
-     * Precondition: q != null.
+     * Precondition: other != null.
      */
-    public BodyQueue(BodyQueue q) {
-        this.capacity = q.capacity;
-        this.head = q.size();
+    public BodyQueue(BodyQueue other) {
+        this.capacity = other.capacity;
+        this.head = other.size();
         this.tail = 0;
         this.queue = new Body[this.capacity];
-        for (int i = 0; i < q.size(); i++) {
-            this.queue[i] = q.queue[i];
+        for (int i = 0, j = other.tail; i < this.head; i++, j++) {
+            this.queue[i] = other.queue[j % other.capacity];
         }
     }
 
@@ -43,12 +43,11 @@ public class BodyQueue {
      * Adds the specified body 'b' to this queue.
      */
     public void add(Body b) {
+        if ((head + 1) % capacity == tail) {
+            doubleCapacity();
+        }
         queue[head] = b;
         head = (head + 1) % capacity;
-        if (head == tail) {
-            doubleCapacity();
-            head = capacity / 2;
-        }
     }
 
     /**
@@ -57,6 +56,8 @@ public class BodyQueue {
      */
     public Body poll() {
         if (tail == head) {
+            tail = 0;
+            head = 0;
             return null;
         }
         Body b = queue[tail];
@@ -77,10 +78,10 @@ public class BodyQueue {
      */
     private void doubleCapacity() {
         Body[] tmp = new Body[capacity * 2];
-        for (int i = head, j = 0; i < tail + capacity; i++, j++) {
-            tmp[j] = queue[i % capacity];
+        head = size();
+        for (int i = 0, j = tail; i < head; i++, j++) {
+            tmp[i] = queue[j % capacity];
         }
-        head = capacity;
         tail = 0;
         capacity *= 2;
         queue = tmp;

src/Simulation.java

@@ -81,7 +81,7 @@ public class Simulation {
             // merge bodies that have collided
             for (int i = 0; i < bodies.length; i++) {
                 for (int j = i + 1; j < bodies.length; j++) {
-                    if (bodies[j].distanceTo(bodies[i]) < bodies[j].radius() + bodies[i].radius()) {
+                    if (bodies[j].collidesWith(bodies[i])) {
                         bodies[i] = bodies[i].merge(bodies[j]);
                         Body[] bodiesOneRemoved = new Body[bodies.length - 1];
                         for (int k = 0; k < bodiesOneRemoved.length; k++) {

src/Simulation3.java

@@ -1,11 +1,74 @@
-// Simulates the formation of a massive solar system.
-//
+import codedraw.CodeDraw;
+
+import java.awt.*;
+import java.util.Random;
+
+/**
+ * Simulates the formation of a massive solar system.
+ */
 public class Simulation3 {
 
-    // The main simulation method using instances of other classes.
+    /**
+     * The main simulation method using instances of other classes.
+     */
     public static void main(String[] args) {
+        CodeDraw cd = new CodeDraw();
+        BodyLinkedList bodies = new BodyLinkedList();
+        BodyForceTreeMap forceOnBody = new BodyForceTreeMap();
 
-        //TODO: change implementation of this method according to 'Aufgabenblatt3.md'.
+        Random random = new Random(2022);
 
+        for (int i = 0; i < Simulation.NUMBER_OF_BODIES; i++) {
+            bodies.addLast(new Body(
+                    Math.abs(random.nextGaussian()) * Simulation.OVERALL_SYSTEM_MASS / Simulation.NUMBER_OF_BODIES,
+                    new Vector3(
+                            0.2 * random.nextGaussian() * Simulation.AU,
+                            0.2 * random.nextGaussian() * Simulation.AU,
+                            0.2 * random.nextGaussian() * Simulation.AU
+                    ),
+                    new Vector3(
+                            0 + random.nextGaussian() * 5e3,
+                            0 + random.nextGaussian() * 5e3,
+                            0 + random.nextGaussian() * 5e3
+                    )
+            ));
+        }
+
+        long seconds = 0;
+        while (true) {
+            seconds++;
+
+            BodyLinkedList mergedBodies = new BodyLinkedList();
+            for (Body b1 : bodies) {
+                BodyLinkedList colliding = bodies.removeCollidingWith(b1);
+                for (Body b2 : colliding) {
+                    b1 = b1.merge(b2);
+                }
+                mergedBodies.addLast(b1);
+            }
+            bodies = mergedBodies;
+
+            for (Body b1 : bodies) {
+                Vector3 force = new Vector3();
+                for (Body b2 : bodies) {
+                    if (b1 != b2) {
+                        force = force.plus(b1.gravitationalForce(b2));
+                    }
+                }
+                forceOnBody.put(b1, force);
+            }
+
+            for (Body body : bodies) {
+                body.move(forceOnBody.get(body));
+            }
+
+            if ((seconds % 3600) == 0) {
+                cd.clear(Color.BLACK);
+                for (Body body : bodies) {
+                    body.draw(cd);
+                }
+                cd.show();
+            }
+        }
     }
 }

src/SolSystem.java

@@ -0,0 +1,7 @@
+public class SolSystem {
+    public static final Body SUN = new Body(1.989e30, new Vector3(0, 0, 0), new Vector3(0, 0, 0));
+    public static final Body EARTH = new Body(5.972e24, new Vector3(-1.394555e11, 5.103346e10, 0), new Vector3(-10308.53, -28169.38, 0));
+    public static final Body MERCURY = new Body(3.301e23, new Vector3(-5.439054e10, 9.394878e9, 0), new Vector3(-17117.83, -46297.48, -1925.57));
+    public static final Body VENUS = new Body(4.86747e24, new Vector3(-1.707667e10, 1.066132e11, 2.450232e9), new Vector3(-34446.02, -5567.47, 2181.10));
+    public static final Body MARS = new Body(6.41712e23, new Vector3(-1.010178e11, -2.043939e11, -1.591727E9), new Vector3(20651.98, -10186.67, -2302.79));
+}

src/SpaceDraw.java

@@ -8,7 +8,6 @@ public class SpaceDraw {
      * where m and r measured in solar units.)
      */
     public static double massToRadius(double mass) {
-
         return Simulation.SUN_RADIUS * (Math.pow(mass / Simulation.SUN_MASS, 0.5));
     }
 
@@ -34,7 +33,6 @@ public class SpaceDraw {
      * Returns the approximate color of temperature 'kelvin'.
      */
     private static Color kelvinToColor(int kelvin) {
-
         double k = kelvin / 100D;
         double red = k <= 66 ? 255 : 329.698727446 * Math.pow(k - 60, -0.1332047592);
         double green = k <= 66 ? 99.4708025861 * Math.log(k) - 161.1195681661 : 288.1221695283 * Math.pow(k - 60, -0.0755148492);
@@ -51,12 +49,15 @@ public class SpaceDraw {
      * A transformation used in the method 'kelvinToColor'.
      */
     private static int limitAndDarken(double color, int kelvin) {
-
         int kelvinNorm = kelvin - 373;
-
-        if (color < 0 || kelvinNorm < 0) return 0;
-        else if (color > 255) return 255;
-        else if (kelvinNorm < 500) return (int) ((color / 256D) * (kelvinNorm / 500D) * 256);
-        else return (int) color;
+        if (color < 0 || kelvinNorm < 0) {
+            return 0;
+        } else if (color > 255) {
+            return 255;
+        } else if (kelvinNorm < 500) {
+            return (int) ((color / 256D) * (kelvinNorm / 500D) * 256);
+        } else {
+            return (int) color;
+        }
     }
 }

src/Vector3.java

@@ -4,7 +4,6 @@ import codedraw.CodeDraw;
  * This class represents vectors in a 3D vector space.
  */
 public class Vector3 {
-
     private double x;
     private double y;
     private double z;
@@ -23,37 +22,29 @@ public class Vector3 {
         this.z = z;
     }
 
+    public Vector3(Vector3 other) {
+        this(other.x, other.y, other.z);
+    }
+
     /**
      * Returns the sum of this vector and vector 'v'.
      */
     public Vector3 plus(Vector3 v) {
-        Vector3 result = new Vector3();
-        result.x = x + v.x;
-        result.y = y + v.y;
-        result.z = z + v.z;
-        return result;
+        return new Vector3(x + v.x, y + v.y, z + v.z);
     }
 
     /**
      * Returns the product of this vector and 'd'.
      */
     public Vector3 times(double d) {
-        Vector3 result = new Vector3();
-        result.x = x * d;
-        result.y = y * d;
-        result.z = z * d;
-        return result;
+        return new Vector3(x * d, y * d, z * d);
     }
 
     /**
      * Returns the sum of this vector and -1*v.
      */
     public Vector3 minus(Vector3 v) {
-        Vector3 result = new Vector3();
-        result.x = x - v.x;
-        result.y = y - v.y;
-        result.z = z - v.z;
-        return result;
+        return new Vector3(x - v.x, y - v.y, z - v.z);
     }
 
     /**
@@ -85,22 +76,38 @@ public class Vector3 {
         z /= length;
     }
 
+    public double getScreenX(CodeDraw cd) {
+        return cd.getWidth() * (this.x + Simulation.SECTION_SIZE / 2) / Simulation.SECTION_SIZE;
+    }
+
+    public double getScreenY(CodeDraw cd) {
+        return cd.getWidth() * (this.y + Simulation.SECTION_SIZE / 2) / Simulation.SECTION_SIZE;
+    }
+
     /**
      * Draws a filled circle with a specified radius centered at the (x,y) coordinates of this vector
      * in the canvas associated with 'cd'. The z-coordinate is not used.
      */
     public void drawAsFilledCircle(CodeDraw cd, double radius) {
-        double x = cd.getWidth() * (this.x + Simulation.SECTION_SIZE / 2) / Simulation.SECTION_SIZE;
-        double y = cd.getWidth() * (this.y + Simulation.SECTION_SIZE / 2) / Simulation.SECTION_SIZE;
         radius = cd.getWidth() * radius / Simulation.SECTION_SIZE;
-        cd.fillCircle(x, y, Math.max(radius, 1.5));
+        cd.fillCircle(getScreenX(cd), getScreenY(cd), Math.max(radius, 1.5));
     }
 
     /**
      * Returns the coordinates of this vector in brackets as a string
      * in the form "[x,y,z]", e.g., "[1.48E11,0.0,0.0]".
      */
+    @Override
     public String toString() {
-        return String.format("[%f,%f,%f]", x, y, z);
+        return String.format("[%g,%g,%g]", x, y, z);
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other.getClass() != Vector3.class) {
+            return false;
+        }
+        Vector3 v = (Vector3) other;
+        return this.x == v.x && this.y == v.y && this.z == v.z;
     }
 }