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📜  使用示例在Java中设置 removeAll() 方法

📅  最后修改于: 2022-05-13 01:54:27.582000             🧑  作者: Mango

使用示例在Java中设置 removeAll() 方法

Java.util.Set接口的removeAll()方法用于从该集合中删除指定集合中包含的所有元素。

句法:

public boolean removeAll(Collection c)

参数:此方法将集合 c作为包含要从此集合中删除的元素的参数。

返回值:如果此集合因调用而更改,则此方法返回true

异常:如果此集合包含空元素并且指定的集合不允许空元素(可选),或者指定的集合为空,则此方法抛出NullPointerException

下面是说明removeAll()方法的示例。

示例 1:

// Java program to demonstrate
// removeAll() method for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
  
        try {
            // Creating object of Set
            Set set1 = new HashSet();
  
            // Populating set1
            set1.add(1);
            set1.add(2);
            set1.add(3);
            set1.add(4);
            set1.add(5);
  
            // print set1
            System.out.println("Set before removeAll() operation : "
                               + set1);
  
            // Creating another object of Set
            Set set2 = new HashSet();
            set2.add(1);
            set2.add(2);
            set2.add(3);
  
            // print set2
            System.out.println("Collection Elements to be removed : "
                               + set2);
  
            // Removing elements from set
            // specified in set2
            // using removeAll() method
            set1.removeAll(set2);
  
            // print set1
            System.out.println("Set after removeAll() operation : "
                               + set1);
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}
输出:
Set before removeAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be removed : [1, 2, 3]
Set after removeAll() operation : [4, 5]

示例 2:对于NullPointerException

// Java program to demonstrate
// removeAll() method for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
  
            // Creating object of Set
            Set set1 = new HashSet();
  
            // Populating set1
            set1.add(1);
            set1.add(2);
            set1.add(3);
            set1.add(4);
            set1.add(5);
  
            // print set1
            System.out.println("Set before removeAll() operation : "
                               + set1);
  
            // Creating another object of Set
            Set set2 = null;
  
            // print set2
            System.out.println("Collection Elements to be removed : "
                               + set2);
  
            System.out.println("\nTrying to pass "
                               + "null as a specified element\n");
  
            // Removing elements from set
            // specified in set2
            // using removeAll() method
            set1.removeAll(set2);
  
            // print set1
            System.out.println("Set after removeAll() operation : "
                               + set1);
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}
输出:
Set before removeAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be removed : null

Trying to pass null as a specified element

Exception thrown : java.lang.NullPointerException

参考:https: Java Java.util.Collection)