一个简单的问题

Question

用数组实现堆栈(stack)的方法

Answer 1

使用Stack类啊,自己看看Stack类

Answer 2

public class MyStack {
        Object[] obj = new Object[1];
        public void push(Object o) {
                if (obj[0] != null) { //判断是否为空，数组不为空，数组大小加一，插入
                        Object[] temp = obj; //temp用来临时保存，复制
                        obj = new Object[obj.length + 1];
                        for (int j = 0; j < temp.length; j++) {
                                obj[j] = temp[j];
                        }
                        temp = null;
                        obj[obj.length - 1] = o; //在末尾插入
                }
                else {
                        obj[0] = o; //数组为空，插入到首位
                }
        }
        public Object pop() {
                if (obj[0]!=null){ //判断数组非空，取值
                        Object o = obj[obj.length - 1];
                        Object[] temp = obj; //temp用来临时保存，复制
                        obj = new Object[obj.length - 1]; //数组长度减一
                        for (int j = 0; j < temp.length-1; j++) {
                                obj[j] = temp[j];
                        }
                        temp = null;
                        return o;
                }                                        
                else { 
                        return null; //数组为空，不返回
                }
        }
        public int search(Object o){
                if(o!=null){
                        for(int i=0;i<obj.length;i++){
                                if(obj[i].equals(o))return i;                                        
                        }
                        return -1;
                }
                else{
                        return -1;
                }
        }
        public static void main(String[] args) {
                MyStack myStack = new MyStack();
                myStack.push(new String("abc"));
                myStack.push(new String("cba"));
                myStack.push(new Integer(111));
                myStack.push(new Integer(222));
                
                for (int i = 0; i < myStack.obj.length; i++) {
                        System.out.println(myStack.obj[i]);
                }
                System.out.println("**********");
                Object o1 = myStack.pop();
                Object o2 = myStack.pop();
                Object o3 = myStack.pop();
                
                System.out.println(o1);
                System.out.println(o2);
                System.out.println(o3);
                System.out.println("**********");
                for (int i = 0; i < myStack.obj.length; i++) {
                                        System.out.println(myStack.obj[i]);
                }                
        }
} 不过数组有大小限制