本文目录一览：

1. 用java编写程序，使用文件输出流，向文件分别写入如下类型的数据：int、double和字符串
2. java中怎样把double类型和当前时间用IO流写入到文件txt中?、
3. java写double入txt 3 6 7 为什么不一样了

用java编写程序，使用文件输出流，向文件分别写入如下类型的数据：int、double和字符串

import java.io.*;
class Test {
    public static void main(String args[]) throws IOException {
        writeData();
    }
    public static void writeData() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        DataOutputStream dos = new DataOutputStream(new FileOutputStream("data.txt"));
        BufferedWriter bw = new BufferedWriter(new FileWriter("data.txt"));
        String line = null;
        while ((line = br.readLine()) != null) {
            if (line.equals("exit")) // 录入的字符串是"exit"，则退出
                break;
            try {
                dos.writeInt(Integer.parseInt(line)); // 如果录入的是int型，则向文件“data.txt”中写入int型的数据
            } catch (NumberFormatException e1) {
                try {
                    dos.writeDouble(Double.parseDouble(line)); // 录入的是double型，“data.txt”中写入double型的数据
                } catch (NumberFormatException e2) {
                    bw.write(line); // 不是int，double，即使String类型，就将String类型写入
                }
            }
        }
        br.close();
        dos.close();
        bw.close();
    }
}

java中怎样把double类型和当前时间用IO流写入到文件txt中?、

package com.winjing.testing.utils;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Test {
    /**
     * @param args
     */
    public static void main(String[] args) {
        PrintWriter pw;
        try {
            Double num = 1.2;
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            String time = format.format(new Date());
            pw = new PrintWriter(new FileWriter("D:\\test.txt"));
            pw.print(num + "\t" + time);
            pw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public void DOWriteTxt(String file, String txt) {
        try {
            FileOutputStream os = new FileOutputStream(new File(file), true);
            os.write((txt + "\n").getBytes());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

java写double入txt 3 6 7 为什么不一样了

对于double类型的 做 一下精度处理

import java.io.IOException;
import java.io.RandomAccessFile;
public class Test {
    public static void main(String[] args) throws IOException {
        RandomAccessFile rf = new RandomAccessFile("D://java.txt", "rw");
        String s = "";
        for (int i = 0; i < 10; i++) {
            s = String.valueOf(i);
            s = s + "\r\n ";
            rf.writeBytes(s);
        }
        for (int i = 0; i < 10; i++) {
            s = String.format("%.1f", (i * 1.1));
            s = s + "\r\n ";
            rf.writeBytes(s);
        }
        // rf.close();
        rf = new RandomAccessFile("D://java.txt", "rw");
        for (int i = 0; i < 20; i++) {
            s = rf.readLine();
            System.out.println("Value " + i + ": " + s);
        }
        rf.close();
    }
}