Java SortedSet removeAll()方法及示例

SortedSet 接口的 removeAll() 方法用于从这个SortedSet中删除其包含在指定集合中的所有元素。
语法

public boolean removeAll(Collection c)

参数： 该方法接受 集合c 作为参数，其中包含要从这个排序集合中删除的元素。
返回值： 如果这个集合因调用而发生变化，该方法返回 true 。
异常： 如果这个集合包含一个空元素，而指定的集合不允许有空元素（可选），或者指定的集合是空的，这个方法会抛出 NullPointerException 。

注：SortedSet中的removeAll()方法是继承自Java中的Set接口。
以下是说明removeAll()方法的例子。
例1 :

// Java program to demonstrate
// removeAll() method for Integer value
 
import java.util.*;
 
public class GFG1 {
    public static void main(String[] args)
        throws Exception
    {
 
        try {
            // Creating object of SortedSet
            SortedSet<Integer> set1
                = new TreeSet<Integer>();
 
            // 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
            SortedSet<Integer> set2
                = new TreeSet<Integer>();
            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]

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[] args)
        throws Exception
    {
        try {
 
            // Creating object of SortedSet
            SortedSet<Integer> set1
                = new TreeSet<Integer>();
 
            // 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 SortedSet<Integer>
            SortedSet<Integer> 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(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

java.lang.NullPointerException

参考资料 : https://docs.oracle.com/javase/7/docs/api/java/util/Set.html#removeAll(java.util.Collection)