Java-StringBuffer和StringBuilder

package com.example.demo.StringTest;

import org.junit.jupiter.api.Test;

import org.springframework.boot.test.context.SpringBootTest;

import java.io.*;

/**

* @author hanqiang

* @Classname StringTest

* @Date 2021/5/20 14:23

* @Description:

*/

@SpringBootTest

public class StringTest {

@Test

public void myTest()throws FileNotFoundException {

StringBuilder stringBuilder=new StringBuilder();

stringBuilder.append("aaa1");

stringBuilder.append(1);

stringBuilder.append(44.0);

stringBuilder.append(33.00);

System.out.println("反转前"+stringBuilder);

//字符串反转

        stringBuilder.reverse();

System.out.println("反转后"+stringBuilder);

StringBuffer stringBuffer=new StringBuffer();

stringBuffer.append("（这是测试数据");

stringBuffer.append(11234567);

try{

FileReader fileWriter=new FileReader("C:\\Users\\Administrator\\Desktop\\1.txt");

BufferedReader bufferedReader=new BufferedReader(fileWriter);

char[] c=new char[20];

while(bufferedReader.read(c)>0){

stringBuffer.append(c);

}

FileWriter fileWriter1=new FileWriter("C:\\Users\\Administrator\\Desktop\\2.txt");

BufferedWriter bufferedWriter=new BufferedWriter(fileWriter1);

bufferedWriter.write(new String(stringBuffer));

bufferedWriter.flush();

bufferedReader.close();

bufferedWriter.close();

}catch(Exception e){

e.printStackTrace();

}

stringBuffer.append("------------------结束）");

stringBuffer.reverse();

System.out.println("#####3333###############："+stringBuffer);

System.out.println();

//当反转之后，字符串一直处于反转状态,反转回来

        stringBuffer.reverse();

System.out.println("从第十个字符串开始截取："+stringBuffer.substring(10));

}

}