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ListQueue.java
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89 lines (62 loc) · 1.42 KB
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import java.util.Iterator;
public class ListQueue<Item> implements MyQueue<Item> {
private Node first;
private Node last;
int N = 0;
private class Node {
Item item;
Node next;
}
@Override
public boolean isEmpty() {
return N == 0;
}
@Override
public int size() {
return N;
}
@Override
public MyQueue<Item> add(Item item) {
Node newNode = new Node();
newNode.item = item;
newNode.next = null;
if (isEmpty()) {
last = newNode;
first = newNode;
} else {
last.next = newNode;
last = newNode;
}
N++;
return this;
}
@Override
public Item remove() throws Exception {
if (isEmpty()) {
throw new Exception("queue is empty");
}
Node node = first;
first = first.next;
N--;
if (isEmpty()) {
last = null;
}
return node.item;
}
@Override
public Iterator<Item> iterator() {
return new Iterator<Item>() {
Node cur = first;
@Override
public boolean hasNext() {
return cur != null;
}
@Override
public Item next() {
Item item = cur.item;
cur = cur.next;
return item;
}
};
}
}