Java.util.ArrayList.contains（）

描述

该java.util.ArrayList.contains（Object）如果此列表包含指定的元素，方法返回true。

声明

以下是java.util.ArrayList.contains（）方法的声明

public boolean contains(Object o)

参数

o - 要测试其在此列表中的存在的元素。

返回值

如果此列表包含指定的元素，则此方法返回true。

异常

NA

实例

以下示例显示了java.util.Arraylist.contains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>(8);

      // use add() method to add elements in the list
      arrlist.add(20);
      arrlist.add(25);
      arrlist.add(10);
      arrlist.add(15);        

      // let us print all the elements available in list
      for (Integer number : arrlist) {
         System.out.println("Number = " + number);
      }

      // list contains element 10
      boolean retval = arrlist.contains(10);

      if (retval == true) {
         System.out.println("element 10 is contained in the list");
      } else {
         System.out.println("element 10 is not contained in the list");
      }

      // list does not contain element 30
      boolean retval2 = arrlist.contains(30);

      if (retval2 == true) {
         System.out.println("element 30 is contained in the list");
      } else {
         System.out.println("element 30 is not contained in the list");    
      }
   }
}

让我们编译并运行上面的程序，这将产生以下结果

Number = 20
Number = 25
Number = 10
Number = 15
element 10 is contained in the list
element 30 is not contained in the list