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 : nullTrying to pass null as a specified elementjava.lang.NullPointerException

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