package com.wzs;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
/**
* list,set,map,数组间的相互转换
*
* @author Administrator
*
*/
public class ChangeTest {
public static void main(String[] args) {
// List-->数组
List<String> list = new ArrayList<String>();
list.add("tom");
list.add("Jerval");
list.add("WeiSi");
Object[] objects = list.toArray();// 返回Object数组
System.out.println("objects:" + Arrays.toString(objects));
String[] strings1 = new String[list.size()];
list.toArray(strings1);// 将转化后的数组放入已经创建好的对象中
System.out.println("strings1:" + Arrays.toString(strings1));
String[] strings2 = list.toArray(new String[0]);// 将转化后的数组赋给新对象
System.out.println("strings2:" + Arrays.toString(strings2));
// 数组-->List
String[] ss = { "JJ", "KK" };
List<String> list1 = Arrays.asList(ss);
List<String> list2 = Arrays.asList("AAA", "BBB");
System.out.println(list1);
System.out.println(list2);
// List-->Set
List<String> list3 = new ArrayList<String>(new HashSet<String>());
// Set-->List
Set<String> set = new HashSet<String>(new ArrayList<String>());
// 数组-->Set
String[] strs = { "AA", "BB" };
Set<String> set2 = new HashSet<String>(Arrays.asList(strs));
System.out.println(set2);
// Set-->数组
Set<String> set3 = new HashSet<String>(Arrays.asList("PP", "OO"));
String[] strSet = new String[set3.size()];
set3.toArray(strSet);
System.out.println(Arrays.toString(strSet));
// Map操作
Map<String, String> map = new HashMap<String, String>();
map.put("YYY", "UUU");
map.put("RRR", "TTT");
// 将键转化为Set
Set<String> mapKeySet = map.keySet();
// 将值转化为Set
Set<String> mapValuesSet = new HashSet<String>(map.values());
// 将值转化为List
List<String> mapValuesList = new ArrayList<String>(map.values());
}
}