读取源文件内容的每一行,求和再存入最后一行

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要求如下：

代码如下：

public class TestDemo7 {public static void main(String[] args) {System.out.println("*****开始****");try{FileInputStream fis = new FileInputStream("pw.txt");InputStreamReader isr = new InputStreamReader(fis,"GBK");BufferedReader br = new BufferedReader(isr);StringBuilder builder = new StringBuilder();String str = null;while( (str = br.readLine())!= null ){builder.append(str);}//追加写FileOutputStream fos = new FileOutputStream("pw.txt",true);fos.write(builder.toString().getBytes("GBK"));br.close();fos.close();} catch (Exception e) {e.printStackTrace();}System.out.println("*****结束****");}}

或者：

public class TestDemo7 {public static void main(String[] args) {System.out.println("*****开始****");try{BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("pw.txt"),"GBK"));StringBuilder builder = new StringBuilder();String str = null;while( (str = br.readLine())!= null ){builder.append(str);}//追加写FileOutputStream fos = new FileOutputStream("pw.txt",true);fos.write(builder.toString().getBytes("GBK"));br.close();fos.close();} catch (Exception e) {e.printStackTrace();}System.out.println("*****结束****");}}

原文件pw.txt中为：

大家好!hello!bye!

程序运行后文件内容为:

大家好!hello!bye!大家好!hello!bye!

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