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 -- 其存在于该列表用来进行测试的元素。

返回值

如果此列表包含指定的元素，此方法返回true。

异常

• NA

例子

下面的示例演示java.util.Arraylist.contains方法的用法。

package com.yiibai;

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");    
       }
   }
}

让我们来编译和运行上面的程序，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