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" })@Testpublic 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" })@Testpublic 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" })@Testpublic 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);}}}