Java List contains()用法及代码示例

Java中的List接口的contains()方法用于检查指定元素是否存在于给定列表中。

用法:

public boolean contains(Object obj)

object-element to be searched for

参数：此方法接受单个参数obj，其在列表中的存在将被测试。

返回值：如果在列表中找到指定的元素，则返回true，否则返回false。

下面的程序在List中说明了contains()方法：

示例1:在整数列表中演示contains()方法的用法。

// Java code to demonstrate the working of 
// contains() method in List interface 
  
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
        // creating an Empty Integer List 
        List<Integer> arr = new ArrayList<Integer>(4); 
  
        // using add() to initialize values 
        // [1, 2, 3, 4] 
        arr.add(1); 
        arr.add(2); 
        arr.add(3); 
        arr.add(4); 
  
        // use contains() to check if the element 
        // 2 exits or not 
        boolean ans = arr.contains(2); 
  
        if (ans) 
            System.out.println("The list contains 2"); 
        else
            System.out.println("The list does not contains 2"); 
  
        // use contains() to check if the element 
        // 5 exits or not 
        ans = arr.contains(5); 
  
        if (ans) 
            System.out.println("The list contains 5"); 
        else
            System.out.println("The list does not contains 5"); 
    } 
}

输出：

The list contains 2
The list does not contains 5

示例2:在字符串列表中演示方法contains()的工作。

// Java code to demonstrate the working of 
// contains() method in List of string 
  
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
        // creating an Empty String List 
        List<String> arr = new ArrayList<String>(4); 
  
        // using add() to initialize values 
        // ["geeks", "for", "geeks"] 
        arr.add("geeks"); 
        arr.add("for"); 
        arr.add("geeks"); 
  
        // use contains() to check if the element 
        // "geeks" exits or not 
        boolean ans = arr.contains("geeks"); 
  
        if (ans) 
            System.out.println("The list contains geeks"); 
        else
            System.out.println("The list does not contains geeks"); 
  
        // use contains() to check if the element 
        // "coding" exits or not 
        ans = arr.contains("coding"); 
  
        if (ans) 
            System.out.println("The list contains coding"); 
        else
            System.out.println("The list does not contains coding"); 
    } 
}

输出：

The list contains geeks
The list does not contains coding

实际应用：在搜索操作中，我们可以检查列表中是否存在给定元素。

参考： https://docs.oracle.com/javase/7/docs/api/java/util/List.html#contains(java.lang.Object)

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注：本文由纯净天空筛选整理自gopaldave大神的英文原创作品 List contains() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。