Java Stack peek()用法及代码示例

Java中的java.util.Stack.peek()方法用于检索或获取Stack的第一个元素或位于Stack顶部的元素。检索到的元素不会被删除或从堆栈中删除。

用法:

STACK.peek()

参数：该方法不带任何参数。

返回值：该方法返回堆栈顶部的元素，如果堆栈为空，则返回NULL。

异常：如果堆栈为空，则该方法引发EmptyStackException。

以下程序说明了java.util.Stack.peek()方法：
示例1:

// Java code to illustrate peek() function 
  
import java.util.*; 
  
public class StackDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty Stack 
        Stack<String> STACK = new Stack<String>(); 
  
        // Use push() to add elements into the Stack 
        STACK.push("Welcome"); 
        STACK.push("To"); 
        STACK.push("Geeks"); 
        STACK.push("For"); 
        STACK.push("Geeks"); 
  
        // Displaying the Stack 
        System.out.println("Initial Stack: " + STACK); 
  
        // Fetching the element at the head of the Stack 
        System.out.println("The element at the top of the"
                           + " stack is: " + STACK.peek()); 
  
        // Displaying the Stack after the Operation 
        System.out.println("Final Stack: " + STACK); 
    } 
}

输出：

Initial Stack: [Welcome, To, Geeks, For, Geeks]
The element at the top of the stack is: Geeks
Final Stack: [Welcome, To, Geeks, For, Geeks]

示例2:

// Java code to illustrate peek() function 
  
import java.util.*; 
  
public class StackDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty Stack 
        Stack<Integer> STACK = new Stack<Integer>(); 
  
        // Use push() to add elements into the Stack 
        STACK.push(10); 
        STACK.push(15); 
        STACK.push(30); 
        STACK.push(20); 
        STACK.push(5); 
  
        // Displaying the Stack 
        System.out.println("Initial Stack: " + STACK); 
  
        // Fetching the element at the head of the Stack 
        System.out.println("The element at the top of the"
                           + " stack is: " + STACK.peek()); 
  
        // Displaying the Stack after the Operation 
        System.out.println("Final Stack: " + STACK); 
    } 
}

输出：

Initial Stack: [10, 15, 30, 20, 5]
The element at the top of the stack is: 5
Final Stack: [10, 15, 30, 20, 5]

相关用法

注：本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 Stack peek() Method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。