Java HashSet clear()
Java HashSet类的
clear()方法用于从该集合中删除所有元素。
语法
以下是
clear()方法的声明:
参数
此方法不接受任何参数。
返回
clear()方法不会返回任何值。
例外:
NA
兼容版本
Java 1.2及更高版本
示例1
import java.util.*;
public class HashSetClearExample1 {
public static void main(String[] args) {
HashSet<String>hset = new HashSet<String>();
hset.add("JTP");
hset.add("SSSIT");
hset.add("DFC");
System.out.println("Hash set Elements: "+ hset);
hset.clear();
System.out.println("Hash set elements after clear: "+ hset);
}
}
输出:
Hash set Elements: [DFC, SSSIT, JTP]
Hash set elements after clear: []
示例2
import java.util.*;
public class HashSetClearExample2 {
public static void main(String[] args) {
HashSet<Integer> hset = new HashSet<Integer>();
hset.add(121);
hset.add(111);
hset.add(151);
System.out.println("Hash set Elements: "+ hset);
hset.clear();
System.out.println("Hash set elements after clear: "+ hset);
}
}
输出:
Hash set Elements: [151, 121, 111]
Hash set elements after clear: []
示例3
import java.util.*;
public class HashSetClearExample3 {
public static void main(String[] args) {
HashSet<String> hset1 = new HashSet<String>();
HashSet hset1.add("Facebook");
hset1.add("Twitter");
hset1.add("Instagram");
hset1.add("Google");
System.out.println("Size of the HashSet: "+hset1.size());
System.out.println("Elements of the HashSet before clear:");
for(String val : hset1)
{
System.out.println(val);
}
hset1.clear();
System.out.println("Elements of the HashSet after clear:");
System.out.println("Size of the hashset: "+hset1.size());
for(String val : hset1)
{
System.out.println(val);
}
}
}
输出:
Size of the HashSet: 4
Elements of the HashSet before clear:
Google
Twitter
Instagram
Facebook
Elements of the HashSet after clear:
Size of the hashset: 0