怎么用Java 的 IO 改写txt文件中第四行的数据, 帮我实现一下吧!我做不出来 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 for exampleBufferedReader br = new BufferedReader(new FileReader("test.txt"));PrintStream ps = new PrintStream(new FileOutputStream("test.txt.new"));String buf;int count = 0;while ((buf=br.readLine()) != null) { count++; if (count == 4) { buf = buf.replaceAll("xxx", "yyy"); } ps.println(buf);}br.close();ps.close();File f1 = new File("test.txt");f1.delete();File f2 = new File("test.txt.new");f2.renameTo(f1); code=Java]public class Test { public static void main(String[] args) throws IOException { BufferedReader in=new BufferedReader(new FileReader("./src/test.txt")); BufferedWriter out = new BufferedWriter(new FileWriter("./src/test.txt")); String s; int i=0; while((s=in.readLine())!=null){ i++; System.out.println(s); //System.out.println(); if(i==3){ out.write("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"); out.flush(); out.close(); } } in.close(); }}[/code]写不进去呀? applet全局变量的问题 急求解答 用Java做一个聊天程序! 帮忙看个程序~~ 求助:多线程问题 命令行参数问题 求JDK1.4 API文档一份 在java中如何把左中括号"["当成一个普通的字符?我想replaceAll("[","")出错 java程序分数类由一点问题,求教啊 JDBC效率问题,才2,3张表连接查询就慢得受不了?高分求解...... 输出101~200的质数(请问这个if (!f)是什么意思啊?) 在main函数里传进来一个String,往第二个类里传那个赋值于一个String变量,在第三个类里头再使用那个String变量。怎么写?
BufferedReader br = new BufferedReader(new FileReader("test.txt"));
PrintStream ps = new PrintStream(new FileOutputStream("test.txt.new"));
String buf;
int count = 0;
while ((buf=br.readLine()) != null) {
count++;
if (count == 4) {
buf = buf.replaceAll("xxx", "yyy");
}
ps.println(buf);
}
br.close();
ps.close();
File f1 = new File("test.txt");
f1.delete();
File f2 = new File("test.txt.new");
f2.renameTo(f1);
BufferedReader in=new BufferedReader(new FileReader("./src/test.txt"));
BufferedWriter out = new BufferedWriter(new FileWriter("./src/test.txt"));
String s;
int i=0;
while((s=in.readLine())!=null){
i++;
System.out.println(s);
//System.out.println();
if(i==3){
out.write("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
out.flush();
out.close();
}
}
in.close();
}
}[/code]写不进去呀?