Java ArrayList contains()方法

java.util.ArrayList.contains(Object) 如果ArrayList包含指定的元素方法返回true。

1 语法

public boolean contains(Object o)

2 参数

o：要测试其是否存在于ArrayList中的元素。

3 返回值

如果ArrayList包含指定的元素，则此方法返回true。

4 示例 

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * java.util.ArrayList.contains(Object)方法的例子
 */
import java.util.ArrayList;

public class Demo {

    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");
        }
    }
}

输出结果为：

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