Java.util.ArrayList.clear() Java.util.ArrayList.addAll() Java.util.ArrayList.clone() 描述 该java.util.ArrayList.clear()方法移除此调用返回后,所有从这个list.The列表中的元素将是空的。 声明 以下是java.util.ArrayList.clear()方法的声明 public void clear() 参数 NA 返回值 此方法不返回任何值。 异常 NA 实例 以下示例显示了java.util.Arraylist.clear()方法的用法。 package com.tutorialspoint; import java.util.ArrayList; public class ArrayListDemo { public static void main(String[] args) { // create an empty array list with an initial capacity ArrayList<Integer> arrlist = new ArrayList<Integer>(5); // use add() method to add elements in the list arrlist.add(20); arrlist.add(30); arrlist.add(10); arrlist.add(50); // let us print all the elements available in list for (Integer number : arrlist) { System.out.println("Number = " + number); } // finding size of this list int retval = arrlist.size(); System.out.println("List consists of "+ retval +" elements"); System.out.println("Performing clear operation !!"); arrlist.clear(); retval = arrlist.size(); System.out.println("Now, list consists of "+ retval +" elements"); } } 让我们编译并运行上面的程序,这将产生以下结果 Number = 20 Number = 30 Number = 10 Number = 50 List consists of 4 elements Performing clear operation !! Now, list consists of 0 elements Java.util.ArrayList.addAll() Java.util.ArrayList.clone()