用数组实现大小固定的队列和栈

用数组实现大小固定的队列和栈

1、用数组实现大小固定的栈

public class ArrayStack{
	private Integer[] arr;
	public Integer index;
	
	public ArrayStack(int initSize) {
		if(initSize<0) {
			throw new IllegalArgumentException("The init size is less than 0");
		}		
		arr=new Integer[initSize];
		index=0;
	}
	//取栈顶元素
	public Integer peek() {
		if(index==0)
			return null;
		return arr[index-1];
	}
	//压栈
	public void push(int obj) {
		if(index==arr.length){
			throw new ArrayIndexOutOfBoundsException("The stack is full");
		}
		arr[index++]=obj;
	}
	//弹栈顶元素
	public Integer pop() {
		if(index==0) {
			throw new ArrayIndexOutOfBoundsException("The stack is empty");
		}
		return arr[--index];
	}
	public static void main(String[] args) {
		ArrayStack t=new ArrayStack(7);
		t.push(1);
		t.push(3);
		t.push(5);
		t.push(7);
		System.out.println(t.peek());
		System.out.println(t.pop());
	}
		
}

输出：
7
7

2、用数组实现大小固定的队列

public class ArrayQueue{
	private Integer[] arr;
	public Integer size;
	public Integer start;
	public Integer end;
	
	public ArrayQueue(int initSize) {
		if(initSize<0) {
			throw new IllegalArgumentException("The init size is less than 0");
		}		
		arr=new Integer[initSize];
		size=0;
		start=0;
		end=0;
	}
	public Integer peek() {
		if(size==0)
			return null;
		return arr[start];
	}

	public void push(int obj) {
		if(size==arr.length) {
			throw new ArrayIndexOutOfBoundsException("The queue is full");
		}
		size++;
		arr[end]=obj;
		end=end==arr.length-1?0:end+1;
	}
	
	public Integer poll() {
		if(size==0) {
			throw new ArrayIndexOutOfBoundsException("The queue is empty");
		}
		size--;
		int tmp=start;
		start=start==arr.length-1?0:start+1;
		return arr[tmp];
	}
	public static void main(String[] args) {
		ArrayQueue t=new ArrayQueue(7);
		t.push(1);
		t.push(3);
		t.push(5);
		t.push(7);
		System.out.println(t.poll());
		System.out.println(t.peek());
		System.out.println(t.poll());
		System.out.println(t.peek());
	}
		
}

输出：
1
3
3
5