Java中的CopyOnWriteArrayList removeIf()方法示例

CopyOnWriteArrayList 的 removeIf() 方法根据指定条件从此 CopyOnWriteArrayList 中移除元素。

语法：

public boolean removeIf (Predicate<E> filter)

参数： 该方法接受一个必需的参数，filter，它是基于该参数从该列表中删除元素的谓词值。

返回值： 如果 CopyOnWriteArrayList 被更改，则该方法返回一个 布尔值 ，例如 true。否则，该方法返回 false。

异常： 如果指定的谓词 filter 为空，此方法会抛出 NullPointerException 。

下面的程序示例了 CopyOnWriteArrayList 类的 removeIf() 函数：

// Java Program to illustrate the CopyOnWriteArrayList
// removeIf() 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(2);
        ArrLis.add(3);
        ArrLis.add(4);
        ArrLis.add(7);
        ArrLis.add(6);
        ArrLis.add(9);
  
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: "
                           + ArrLis);
  
        // if a number in the List is
        // divisible by 3, then remove it
        ArrLis.removeIf(number -> number % 3 == 0);
  
        // print updated CopyOnWriteArrayList
        System.out.println("Updated CopyOnWriteArrayList: "
                           + ArrLis);
    }
}

CopyOnWriteArrayList: [2, 3, 4, 7, 6, 9]
Updated CopyOnWriteArrayList: [2, 4, 7]

// Java Program to illustrate the CopyOnWriteArrayList
// removeIf() 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("GeeksforGeeks");
        ArrLis.add("GFG");
        ArrLis.add("Geeks");
        ArrLis.add("Gfg");
  
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: "
                           + ArrLis);
  
        try {
  
            // This will throw NullPointerException
            ArrLis.removeIf(null);
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

CopyOnWriteArrayList: [GeeksforGeeks, GFG, Geeks, Gfg]
java.lang.NullPointerException

参考文献：https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/CopyOnWriteArrayList.html#removeIf-java.util.function.Predicate-