j2se util常用类的一个小问题
来源:百度知道 编辑:UC知道 时间:2024/05/16 13:18:08
发一下源代码,我的目的就是想让一个 包含几个字符的HashSet 转换成字符数组。 就是要使被我注释掉的那行代码 运行。
code:
import java.util.*;
public class En{
public static void main(String []args){
Set sa = new HashSet();
Set sb = new HashSet();
sa.add('a');sa.add('b');sa.add('c');
sb.add('b');sb.add('c');sb.add('d');
Set sn = new HashSet(sa);
sn.retainAll(sb);
Set sm = new HashSet(sa);
sm.addAll(sb);
System.out.println(sn);
System.out.println(sm);
System.out.println(sa.isEmpty());
System.out.println(sb.hashCode());
System.out.println(sn.contains('c'));
System.out.println(sn.size());
for( Iterator ir = sm.iterator(); ir.hasNext();)
{ char sw=(Character)ir.next();
System.out.println(sw);
}
//Character[] arr = (Character[])sm.toArray();
System.out.println(arr);
public class En {
public static void main(String[] args) {
ArrayList<Character> sa = new ArrayList<Character>();
ArrayList<Character> sb = new ArrayList<Character>();
sa.add('a');
sa.add('b');
sa.add('c');
sb.add('b');
sb.add('c');
sb.add('d');
ArrayList sn = new ArrayList(sa);
sn.retainAll(sb);
ArrayList<Character> sm = new ArrayList<Character>(sa);
sm.addAll(sb);
System.out.println(sn);
System.out.println(sm);
System.out.println(sa.isEmpty());
System.out.println(sb.hashCode());
System.out.println(sn.contains('c'));
System.out.println(sn.size());
for (Iterator ir = sm.iterator(); ir.hasNext();) {
char sw = (Character) i