Java Stack empty()方法

Java中的java.util.Stack.empty()方法是用来检查一个堆栈是否为空。该方法是布尔类型的，如果堆栈是空的，则返回真，否则返回假。

语法

STACK.empty()

参数： 该方法不接受任何参数。

返回值： 如果堆栈是空的，该方法返回布尔值true，否则返回false。

下面的程序说明了java.util.Stack.empty()方法的工作：

程序1 :

// Java code to demonstrate empty() method
import java.util.*;
  
public class Stack_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty Stack
        Stack<String> STACK = new Stack<String>();
  
        // Stacking strings
        STACK.push("Geeks");
        STACK.push("4");
        STACK.push("Geeks");
        STACK.push("Welcomes");
        STACK.push("You");
  
        // Displaying the Stack
        System.out.println("The stack is: " + STACK);
  
        // Checking for the emptiness of stack
        System.out.println("Is the stack empty? " + 
                                      STACK.empty());
  
        // Popping out all the elements
        STACK.pop();
        STACK.pop();
        STACK.pop();
        STACK.pop();
        STACK.pop();
  
        // Checking for the emptiness of stack
        System.out.println("Is the stack empty? " + 
                                     STACK.empty());
    }
}

输出：

The stack is: [Geeks, 4, Geeks, Welcomes, You]
Is the stack empty? false
Is the stack empty? true

示例2

// Java code to demonstrate empty() method
import java.util.*;
  
public class Stack_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty Stack
        Stack<Integer> STACK = new Stack<Integer>();
  
        // Stacking int values
        STACK.push(8);
        STACK.push(5);
        STACK.push(9);
        STACK.push(2);
        STACK.push(4);
  
        // Displaying the Stack
        System.out.println("The stack is: " + STACK);
  
        // Checking for the emptiness of stack
        System.out.println("Is the stack empty? " + 
                                      STACK.empty());
    }
}

输出：

The stack is: [8, 5, 9, 2, 4]
Is the stack empty? false