Java CopyOnWriteArraySet add()方法

CopyOnWriteArraySet 的 add(E e) 方法将参数中传递的元素插入到Set的末尾或Set中的指定索引处。该函数在向Set中添加新元素时返回true。

语法

public boolean add(E e)

参数： 该函数接受一个强制性的参数 元素 ，指定要在Set中添加的元素。

返回值： 该函数在Set中添加时返回true。

下面的程序说明了上述函数。

程序1 :

// Java Program to illustrate the CopyOnWriteArraySet
// add(element) 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<Integer> ArrSet
            = new CopyOnWriteArraySet<Integer>();
  
        // Add elements
        ArrSet.add(2);
        ArrSet.add(3);
        ArrSet.add(4);
        ArrSet.add(7);
  
        // print CopyOnWriteArraySet
        System.out.println("CopyOnWriteArraySet: "
                           + ArrSet);
  
        // 4 is already present hence cannot add
        System.out.println("On adding 4 it returns "
                           + ArrSet.add(4));
  
        // print CopyOnWriteArraySet
        System.out.println("Updated CopyOnWriteArraySet: "
                           + ArrSet);
    }
}

输出。

CopyOnWriteArraySet: [2, 3, 4, 7]
On adding 4 it returns false
Updated CopyOnWriteArraySet: [2, 3, 4, 7]

程序2

// Java Program to illustrate the CopyOnWriteArraySet
// add(element) 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<Integer> ArrSet
            = new CopyOnWriteArraySet<Integer>();
  
        // Add elements
        ArrSet.add(2);
        ArrSet.add(3);
        ArrSet.add(3);
        ArrSet.add(3);
  
        // print CopyOnWriteArraySet
        System.out.println("CopyOnWriteArraySet: "
                           + ArrSet);
  
        // 45 is not present hence add
        System.out.println("On adding 45 it returns "
                           + ArrSet.add(45));
  
        // print CopyOnWriteArraySet
        System.out.println("Updated CopyOnWriteArraySet: "
                           + ArrSet);
    }
}

输出。

CopyOnWriteArraySet: [2, 3]
On adding 45 it returns true
Updated CopyOnWriteArraySet: [2, 3, 45]

参考资料: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArraySet.html#add-E-