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