java实现栈

public class Test {
	public static void main(String args[]) {
		MyStack<Integer> stack = new MyArrayStack<Integer>();
		
	}
	
	public static interface MyStack<T> {
		boolean isEmpty();
		void clear();
		int length();
		boolean push(T data);
		T pop();
	}
	
	public static class MyArrayStack<T> implements MyStack<T> {
		private Object[] obj = new Object[16];
		private int size = 0;
		@Override
		public boolean isEmpty() {
			return (size == 0);
		}

		@Override
		public void clear() {
			for(int i = 0; i < size; i++) {
				obj[i] = null;
			}
			size = 0;
		}

		@Override
		public int length() {
			return size;
		}

		@Override
		public boolean push(T data) {
			if(size >= obj.length) {
				resize();
			}
			obj[size++] = data;
			return true;
		}
		
		private void resize() {
			Object[] temp = new Object[obj.length + 1];
			for(int i = 0; i < size; i++) {
				temp[i] = obj[i];
				obj[i] = null;
			}
			obj = temp;
		}

		@Override
		public T pop() {
			if(size == 0) {
				return null;
			} else {
				return (T) obj[--size];
			}
		}
		
	}

	public static class MyLinkedStack<T> implements MyStack<T> {
		private Node top;
		private int size;
		
		public MyLinkedStack() {
			top = null;
			size = 0;
		}
		
		@Override
		public boolean isEmpty() {
			return (size == 0);
		}

		@Override
		public void clear() {
			top = null;
			size = 0;
		}

		@Override
		public int length() {
			return size;
		}

		@Override
		public boolean push(T data) {
			Node node = new Node();
			node.data = data;
			node.pre = top;
			top = node;
			size++;
			return true;
		}

		@Override
		public T pop() {
			top = top.pre;
			size--;
			return (T) top.data;
		}
		
		private final class Node {
			private Node pre;
			private T data;
		}
		
		
	}
	

}