list,set,map,数组间的相互转换

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());
	}
}