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)); } }
1 package com.example.demo.StringTest; 2 import org.junit.jupiter.api.Test;import org.springframework.boot.test.context.SpringBootTest; 3 import java.io.*; 4 /** * @author hanqiang * @Classname StringTest * @Date 2021/5/20 14:23 * @Description: */@SpringBootTestpublic class StringTest { @Test public void myTest() throws FileNotFoundException { 5 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); 6 StringBuffer stringBuffer=new StringBuffer(); stringBuffer.append("(这是测试数据"); stringBuffer.append(11234567); 7 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(); 8 bufferedReader.close(); bufferedWriter.close(); 9 }catch(Exception e){ e.printStackTrace(); } 10 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)); }} 11 12