List转换成String字符串三种方式

List转换成String字符串思路分析：
1.List转化成String[],再通过String[]数组遍历拼接成String字符串;
2.List转化成String存到StringBuffer中,再通过StringButter中的append()方法拼接成String字符串;
注意：StringBuffer字符串变量、StringBuilder字符串变量在方式二和方式三种可以把StringBuffer换成StringBuilder，但需要了解二者之间的区别，网址：https://blog.csdn.net/u013131716/article/details/99628104

package com.test01.listtostring;

import java.util.ArrayList;
import java.util.List;
import org.junit.Test;

public class ListToStringTest {
	
	/*
	 * List转换成String字符串
	 * 方式一：
	 * 	分析：List转化成String[],再通过String[]数组遍历拼接成String字符串
	 * 
	 * List内容：[laoyi, laoer, laosan]
	 * 结果：laoyi,laoer,laosan
	 * */
	@SuppressWarnings({ "rawtypes", "unchecked", "unused" })
	@Test
	public void listToString01(){
		
		List list = new ArrayList<>();
		list.add("laoyi");
		list.add("laoer");
		list.add("laosan");
		
		System.out.println("List数组："+list);
		if(list == null && list.size() == 0){
			System.out.println("list中的内容为空！");
		}else{
			
			String[] strArrStrings = new String[list.size()];
			String resultString = "";
			
			for(int i=0;i<=list.size()-1;i++){
				strArrStrings[i] = (String) list.get(i);
			}

			for(int j=0;j<=strArrStrings.length-1;j++){
				if(j < strArrStrings.length-1){
					resultString += strArrStrings[j] + ",";
				}else{
					resultString += strArrStrings[j];	
				}
			}
			System.out.println("最后拼接的字符串：" + resultString);
		}
	}
	
	
	/*
	 * List转换成String字符串
	 * 方式二：
	 * 	分析：List转化成String存到StringBuilder中,再通过StringBuilder中的append()方法拼接成String字符串
	 * 
	 * List内容：[laoyi, laoer, laosan]
	 * 结果：laoyi,laoer,laosan
	 * */
	@SuppressWarnings({ "unused" })
	@Test
	public void listToString03(){
		List<String> list = new ArrayList<>();
		list.add("laoyi");
		list.add("laoer");
		list.add("laosan");
		
		if(null ==list && list.size()<=0){
			System.out.println("list内容为空！");
		}else{
			
			StringBuilder sb = new StringBuilder();
			String resultString = "";
			
			for(int i=0;i<list.size();i++){
				if(i<list.size()-1){
					sb.append(list.get(i));
					sb.append(",");
				}else{
					sb.append(list.get(i));
				}
			}
			
			resultString = sb.toString();
			System.out.println("最后拼接的字符串结果：" + resultString);
		}
	}
	
	/*
	 * List转换成String字符串
	 * 方式三：
	 * 	分析：List转化成String存到StringBuffer中,再通过StringButter中的append()方法拼接成String字符串
	 * 
	 * List内容：[laoyi, laoer, laosan]
	 * 结果：laoyi,laoer,laosan
	 * */
	@SuppressWarnings({ "unused" })
	@Test
	public void listToString02(){
		List<String> list = new ArrayList<>();
		list.add("laoyi");
		list.add("laoer");
		list.add("laosan");
		
		if(null ==list && list.size()<=0){
			System.out.println("list内容为空！");
		}else{
			
			StringBuilder sb = new StringBuilder();
			String resultString = "";
			boolean flag = false;
			for(String str : list){
				if(flag){
					sb.append(",");
				}else{
					flag = true;
				}
				sb.append(str);
			}	
			resultString = sb.toString();
			System.out.println("最后拼接的字符串结果：" + resultString);
		}	
	}
}