Java CopyOnWriteArrayList contains()用法及代碼示例

CopyOnWriteArrayList的contains(E e)方法檢查列表中是否存在給定元素。如果元素至少出現一次，則該函數返回true，否則返回false。

用法:

public boolean contains(Object o)

參數：該函數接受一個強製性參數，該參數指定要在列表中檢查其外觀的元素。

返回值：如果元素在列表中至少出現一次，則該函數返回true，否則返回false。

以下示例程序旨在說明上述函數：

示例1:

// Java Program to illustrate the CopyOnWriteArrayList 
// contains() method in Java 
import java.util.concurrent.CopyOnWriteArrayList; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // create object of CopyOnWriteArrayList 
        CopyOnWriteArrayList<Integer> ArrLis 
            = new CopyOnWriteArrayList<Integer>(); 
  
        // Add elements 
        ArrLis.add(32); 
        ArrLis.add(67); 
        ArrLis.add(98); 
        ArrLis.add(100); 
  
        // print CopyOnWriteArrayList 
        System.out.println("CopyOnWriteArrayList: " + ArrLis); 
  
        // check using function 
        if (ArrLis.contains(100)) 
            System.out.println("100 is present in the list"); 
        else
            System.out.println("100 is not present in the list"); 
  
        // check using function 
        if (ArrLis.contains(20)) 
            System.out.println("20 is present in the list"); 
        else
            System.out.println("20 is not present in the list"); 
    } 
}

輸出：

CopyOnWriteArrayList: [32, 67, 98, 100]
100 is present in the list
20 is not present in the list

示例2:

// Java Program to illustrate the CopyOnWriteArrayList 
// contains() method in Java 
import java.util.concurrent.CopyOnWriteArrayList; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // create object of CopyOnWriteArrayList 
        CopyOnWriteArrayList<String> ArrLis 
            = new CopyOnWriteArrayList<String>(); 
  
        // Add elements 
        ArrLis.add("gopal"); 
        ArrLis.add("gfg"); 
        ArrLis.add("jgec"); 
        ArrLis.add("sudo"); 
  
        // print CopyOnWriteArrayList 
        System.out.println("CopyOnWriteArrayList: " + ArrLis); 
  
        // check using function 
        if (ArrLis.contains("gfg")) 
            System.out.println("'gfg' is present in the list"); 
        else
            System.out.println("'gfg' is not present in the list"); 
  
        // check using function 
        if (ArrLis.contains("best")) 
            System.out.println("'best' is present in the list"); 
        else
            System.out.println("'best' is not present in the list"); 
    } 
}

輸出：

CopyOnWriteArrayList: [gopal, gfg, jgec, sudo]
'gfg' is present in the list
'best' is not present in the list

參考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArrayList.html#contains-E-

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