Java Vector isEmpty() 方法

2025年3月24日 | 阅读时间：2 分钟

Java Vector 类的 isEmpty() 方法用于检查此 Vector 是否没有任何组件。如果 Vector 为空，则返回 true，否则返回 false。

语法

以下是 isEmpty() 方法的声明

参数

此方法不接受任何参数。

当且仅当此 Vector 没有组件时，isEmpty() 方法才返回 true，否则返回 false。

异常

不适用

兼容版本

Java 1.2 及以上版本

示例 1

import java.util.*;
public class VectorIsEmptyExample1 {  
	public static void main(String arg[]) {	
	    //Create an empty vector
	    Vector < String > vec = new Vector < String > ();
	    //Add elements in the vector
	    vec.add("Java");
	    vec.add("Ruby");
	    vec.add("Android");
	    vec.add("Python");
	    //Displaying the Vector
          System.out.println("Vector:  " + vec);
          //Verifying if the Vector is empty or not
          System.out.println("Is the Vector empty? = " +vec.isEmpty());
          //Clear the Vector
          vec.clear(); 
          //Displaying the Vector Again
          System.out.println("Vector after clear(): " +vec); 
          //Verifying if the Vector is empty or not
          System.out.println("Is the Vector empty? = " +vec.isEmpty());
	    }            
}

输出

Vector:  [Java, Ruby, Android, Python]
Is the Vector empty? = false
Vector after clear(): []
Is the Vector empty? = true

示例 2

import java.util.*;
public class VectorIsEmptyExample2 {  
	public static void main(String arg[]) {	
		//Create an empty Vector with initial capacity of 5      
		Vector<Integer> vecObject = new Vector<Integer>(5);	
		//Display the Vector
            System.out.println("Vector: " +vecObject);
            //Verifying if the Vector is empty or not
            System.out.println("Is the Vector empty? = " +vecObject.isEmpty());       
	      }            
}

输出

Vector: []
Is the Vector empty? = true

示例 3

import java.util.*;
public class VectorIsEmptyExample3 {  
	public static void main(String arg[]) {	
	    //Create an empty Vector      
	    Vector < String > colors = new Vector < String > ();
	    //Add color elements in the vector
          colors.add("Red");
          colors.add("Green");
          colors.add("Blue");
          colors.add("Pink");
          //Test the vector if it has no components
          System.out.println("Vector isEmpty() before? " +colors.isEmpty());
          //Remove all elements from the vector
          colors.removeAllElements();
          //Again test the vector if it has no components
          System.out.println("Vector isEmpty() after ? " +colors.isEmpty());      
	    }            
}

输出

Vector isEmpty() before? false
Vector isEmpty() after ? true

下一主题Java Vector

Java Vector isEmpty() 方法

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示例 3

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Java Vector isEmpty() 方法

语法

参数

返回

异常

兼容版本

示例 1

示例 2

示例 3

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