Java 中的 CopyOnWriteArraySet removeAll()方法，带示例

原文:https://www . geeksforgeeks . org/copy onwriterarrayset-removeall-method-in-Java-with-examples/

copy onwriterarrayset方法的 removeAll() 方法删除指定集合中存在的该 copy onwriterarrayset 的所有元素。这意味着这两个集合中常见的元素都将从这个 CopyOnWriteArraySet 中删除。

语法:

public boolean removeAll(Collection<E> c)

参数:该方法接受参数 c ，该参数是包含要从该集合中移除的元素的集合。

返回值:这个方法返回一个布尔值，比如 true，如果 CopyOnWriteArraySet 被改变的话。否则此方法返回 false。

异常:该方法抛出以下异常:

  • ClassCastException :如果这个集合的某个元素的类与指定的集合不兼容
  • NullPointRexception:如果该集合包含空元素，并且指定的集合不允许空元素，或者如果指定的集合为空。

下面的程序说明了 CopyOnWriteArrayList 类的 removeAll()函数:

程序 1:

// Java Program to illustrate the CopyOnWriteArraySet
// removeall() 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(10);
        ArrSet.add(20);
        ArrSet.add(30);
        ArrSet.add(50);

        // print CopyOnWriteArraySet
        System.out.println("CopyOnWriteArraySet: "
                           + ArrSet);

        // create object of ArrayList
        ArrayList<Integer> Arrlist
            = new ArrayList<Integer>();
        // add elements
        Arrlist.add(10);
        Arrlist.add(30);
        Arrlist.add(40);

        // print ArrayList
        System.out.println("ArrayList: " + Arrlist);

        // removing the common elements from
        // the CopyOnWriteArraySet using removeAll()
        System.out.println("Elements removed "
                           + "from CopyOnWriteArraySet: "
                           + ArrSet.removeAll(Arrlist));

        // print updated CopyOnWriteArraySet
        System.out.println("Updated CopyOnWriteArraySet: "
                           + ArrSet);
    }
}

Output:

CopyOnWriteArraySet: [10, 20, 30, 50]
ArrayList: [10, 30, 40]
Elements removed from CopyOnWriteArraySet: true
Updated CopyOnWriteArraySet: [20, 50]

程序 2: 显示空指针异常

// Java Program to illustrate the CopyOnWriteArraySet
// removeall() 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(10);
        ArrSet.add(20);
        ArrSet.add(30);
        ArrSet.add(50);

        // print CopyOnWriteArraySet
        System.out.println("CopyOnWriteArraySet: "
                           + ArrSet);

        try {

            // removing the null from
            // the CopyOnWriteArraySet using removeAll()
            // This will throw NullPointerException

            System.out.println("Elements removed "
                               + "from CopyOnWriteArraySet: "
                               + ArrSet.removeAll(null));
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

Output:

CopyOnWriteArraySet: [10, 20, 30, 50]
java.lang.NullPointerException

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