Java中的 AbstractCollection removeAll() 方法与示例

Java.util.AbstractCollection.removeAll(Collection col)方法用于从 AbstractCollection 中删除指定集合中存在的所有元素。

句法：

AbstractCollection.removeAll(Collection col)

参数：此方法接受一个强制参数col ，该参数是要从 AbstractCollection 中删除其元素的集合。

返回值：如果 AbstractCollection 因操作而改变，则此方法返回true ，否则返回False 。

异常：如果指定的集合为空，该方法将抛出NullPointerException 。

下面的程序说明了Java.util.AbstractCollection.removeAll(Collection col) 方法：

方案一：

// Java code to illustrate removeAll()
import java.util.*;
  
public class AbstractCollectionDemo {
    public static void main(String args[])
    {
  
        // Creating an empty AbstractCollection
        AbstractCollection collection
            = new ArrayList();
  
        // Use add() method to add
        // elements in the AbstractCollection
        collection.add("Geeks");
        collection.add("for");
        collection.add("Geeks");
        collection.add("10");
        collection.add("20");
  
        // Output the AbstractCollection
        System.out.println("AbstractCollection: "
                           + collection);
  
        // Creating an empty AbstractCollection
        AbstractCollection colcollection
            = new ArrayList();
  
        // Use add() method to add
        // elements in the AbstractCollection
        colcollection.add("Geeks");
        colcollection.add("for");
        colcollection.add("Geeks");
  
        // Remove the head using remove()
        boolean changed
            = collection.removeAll(colcollection);
  
        // Print the result
        if (changed)
            System.out.println("Collection removed");
        else
            System.out.println("Collection not removed");
  
        // Print the final AbstractCollection
        System.out.println("Final AbstractCollection: "
                           + collection);
    }
}

输出：

AbstractCollection: [Geeks, for, Geeks, 10, 20]
Collection removed
Final AbstractCollection: [10, 20]

方案二：

// Java code to illustrate removeAll()
import java.util.*;
  
public class AbstractCollectionDemo {
    public static void main(String args[])
    {
  
        // Creating an empty AbstractCollection
        AbstractCollection collection
            = new ArrayList();
  
        // Use add() method to
        // add elements in the AbstractCollection
        collection.add(1);
        collection.add(2);
        collection.add(3);
        collection.add(10);
        collection.add(20);
  
        // Output the AbstractCollection
        System.out.println("AbstractCollection: "
                           + collection);
  
        // Creating an empty AbstractCollection
        AbstractCollection colcollection
            = new ArrayList();
  
        // Use add() method to add elements
        // in the AbstractCollection
        colcollection.add(30);
        colcollection.add(40);
        colcollection.add(50);
  
        // Remove the head using remove()
        boolean changed
            = collection.removeAll(colcollection);
  
        // Print the result
        if (changed)
            System.out.println("Collection removed");
        else
            System.out.println("Collection not removed");
  
        // Print the final AbstractCollection
        System.out.println("Final AbstractCollection: "
                           + collection);
    }
}

输出：

AbstractCollection: [1, 2, 3, 10, 20]
Collection not removed
Final AbstractCollection: [1, 2, 3, 10, 20]