Java中的 CopyOnWriteArraySet contains() 方法

CopyOnWriteArraySet的contains(E e)方法检查给定元素是否存在于 Set 中。

句法：

public boolean contains(Object o)

参数：该函数接受一个强制参数o ，它指定要在 Set 中检查其外观的元素。

返回值：如果元素存在则函数返回true ，否则返回false。

下面的程序说明了上述函数：

方案一：

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

输出：

CopyOnWriteArraySet: [32, 67, 100]
100 is present in the Set
20 is not present in the Set

方案二：

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

输出：

CopyOnWriteArraySet: [geeks, gfg, jgec, sudo]
gfg is present in the Set
best is not present in the Set

参考： https: Java/util/concurrent/CopyOnWriteArraySet.html#contains-java.lang.Object-