java.util.Vector.isEmpty() java.util.Vector.insertElementAt() java.util.Vector.lastElement() 描述 所述isEmpty()方法被用来测试该向量没有组件。 声明 以下是java.util.Vector.isEmpty()方法的声明 public boolean isEmpty() 参数 NA 返回值 当且仅当此向量没有组件时,返回值为true,即其大小为零。否则返回false。 异常 NA 实例 以下示例显示了java.util.Vector.isEmpty()方法的用法。 package com.tutorialspoint; import java.util.Vector; public class VectorDemo { public static void main(String[] args) { // create an empty Vector vec with an initial capacity of 4 Vector<Integer> vec = new Vector<Integer>(4); // let us test the vector System.out.println("The vector does not have any element"); System.out.println("The vector is empty: "+vec.isEmpty()); // use add() method to add elements in the vector vec.add(4); vec.add(3); vec.add(2); vec.add(1); // let us test the vector again System.out.println("The vector has elements"); System.out.println("The vector is empty: "+vec.isEmpty()); } } 让我们编译并运行上面的程序,这将产生以下结果。 The vector does not have any element The vector is empty: true The vector has elements The vector is empty: false java.util.Vector.insertElementAt() java.util.Vector.lastElement()