diff --git a/src/Body.java b/src/Body.java
index 1b6685d..d7b3cc3 100644
--- a/src/Body.java
+++ b/src/Body.java
@@ -106,7 +106,7 @@ public class Body {
      */
     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()
         );
     }
diff --git a/src/BodyForceTreeMap.java b/src/BodyForceTreeMap.java
index 11bab25..752861f 100644
--- a/src/BodyForceTreeMap.java
+++ b/src/BodyForceTreeMap.java
@@ -3,8 +3,8 @@
  * The number of key-value pairs is not limited.
  */
 public class BodyForceTreeMap {
-
-    //TODO: declare variables.
+    private int size = 0;
+    private BodyForceTreeMapItem root = null;
 
     /**
      * Adds a new key-value association to this map. If the key already exists in this map,
@@ -12,7 +12,37 @@ public class BodyForceTreeMap {
      * Precondition: key != null.
      */
     public Vector3 put(Body key, Vector3 value) {
-        //TODO: implement method.
+        if (root == null) {
+            root = new BodyForceTreeMapItem(key, value);
+            size++;
+            return 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;
     }
 
@@ -22,7 +52,16 @@ public class BodyForceTreeMap {
      * 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;
     }
 
@@ -30,16 +69,38 @@ public class BodyForceTreeMap {
      * 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;
     }
 
+    public int size() {
+        return this.size;
+    }
+
+    private String toString(BodyForceTreeMapItem item, String indent) {
+        if (item == null) {
+            return "";
+        }
+        String s = String.format("%s{%s: %s}\n", indent, item.key(), item.value());
+        s += this.toString(item.left(), indent + "| ");
+        s += this.toString(item.right(), indent + "| ");
+        return s;
+    }
+
     /**
      * Returns a readable representation of this map, in which key-value pairs are ordered
      * descending according to the mass of the bodies.
      */
     public String toString() {
-        //TODO: implement method.
-        return null;
+        return toString(root, "");
     }
 }
diff --git a/src/BodyForceTreeMapItem.java b/src/BodyForceTreeMapItem.java
new file mode 100644
index 0000000..a7151e2
--- /dev/null
+++ b/src/BodyForceTreeMapItem.java
@@ -0,0 +1,46 @@
+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;
+    }
+}
diff --git a/src/Simulation3.java b/src/Simulation3.java
index 36d6378..4cdb7c6 100644
--- a/src/Simulation3.java
+++ b/src/Simulation3.java
@@ -14,7 +14,7 @@ public class Simulation3 {
     public static void main(String[] args) {
         CodeDraw cd = new CodeDraw();
         BodyLinkedList bodies = new BodyLinkedList();
-        BodyForceMap forceOnBody = new BodyForceMap();
+        BodyForceTreeMap forceOnBody = new BodyForceTreeMap();
 
         Random random = new Random(2022);
 
diff --git a/src/Vector3.java b/src/Vector3.java
index 93a55e8..2a49656 100644
--- a/src/Vector3.java
+++ b/src/Vector3.java
@@ -94,6 +94,15 @@ public class Vector3 {
      * in the form "[x,y,z]", e.g., "[1.48E11,0.0,0.0]".
      */
     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;
     }
 }