IO读写实例

最新推荐文章于 2025-10-08 22:51:50 发布

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#IO框架 #IO读写实例

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本文介绍了Java中基本类型的读写操作，包括使用DataOutputStream和DataInputStream进行读写；演示了如何通过try-catch-finally结构来捕获并处理IO异常；展示了字符流的桥接方法，即将字节流转换为字符流的过程；最后给出了一个实用的例子，即根据用户输入的文件名，在指定目录下查找文件并进行复制。

基本类型的读写

import java.io.*;

public class TestDataStream {

    public static void main(String[] args) throws IOException {

        OutputStream os = new FileOutputStream("MyFiles\\Data.txt");

        DataOutputStream dos = new DataOutputStream(os);

        dos.writeDouble(3.5);

        dos.close();

        //---------------------------------------------------------

        InputStream is = new FileInputStream("MyFiles\\Data.txt");

        DataInputStream dis = new DataInputStream(is);

        double num = dis.readDouble();

        dis.close();

        System.out.println(num);


    }

}

IO异常捕获

import java.io.*;

public class TestTryCatchFinally {

    public static void main(String[] args) {

        FileOutputStream os = null;
        try {
            os = new FileOutputStream("a.txt");
            os.write('A');
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (os != null) {
                    os.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        // ---------------------------------------------

        InputStream is = null;

        try {
            is = new FileInputStream("a.txt");

            byte[] cache = new byte[32];
            for (;;) {
                int n = is.read(cache);
                if (n == -1) {
                    break;
                }
                for (int i = 0; i < n; i++) {
                    System.out.print((char) cache[i] + "\t");
                }
                System.out.println();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (is != null) {
                    is.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

}

字符的桥接

import java.io*;

public class TestBridgeStream {

    public static void main(String[] args) throws IOException {

        OutputStream os = new FileOutputStream("MyFiles\\Buffered.txt");

        //将字节流转换成字符流
        OutputStreamWriter osw = new OutputStreamWriter(os,"UTF-8");

        PrintWriter pw = new PrintWriter(osw);

        pw.println("人生就像一场戏");
        pw.println("因为有缘才相聚");
        pw.println("相扶到老不容易");
        pw.println("是否更该去珍惜");

        pw.close();

        //描述：
        //流是资源（重量级资源）

//      InputStream is = TestBridgeStream.class.getResourceAsStream("/Buffered.txt");//获取读取TestBridgeStream.class文件时的流对象

        InputStream is = new FileInputStream("MyFiles\\Buffered.txt");

        //将字节流转换成字符流
        InputStreamReader isr = new InputStreamReader(is,"UTF-8");

        BufferedReader br = new BufferedReader(isr);

        for(;;){
            String s = br.readLine();
            if(s == null)
                break;
            System.out.println(s);
        }

        br.close();
    }

}

输入一个文件名,查找并在当前目录复制

import java.io.*;
import java.util.Scanner;

public class TestFileCopy {

    public static void main(String[] args) throws IOException {

        File dir = new File("E:\\Baizhi\\projects\\Question10");

        Scanner input = new Scanner(System.in);

        System.out.print("请输入文件全名:");

        String name = input.next();

        System.out.println("输入为:"+name);

        getFile(dir, name);

        System.out.println("程序结束");

    }

    private static void getFile(File dir, String name) throws IOException {
        File[] file = dir.listFiles();
        if (file == null) {
            System.out.println("文件路径为空!");
            return;
        }
        for (File f : file) {
            if(f.isFile()){
                if(f.getName().equals(name)) {
                    copyFile(f);
                }
            }
            else getFile(f,name);
        }
    }

    private static void copyFile(File f) throws IOException {
        InputStream is = new FileInputStream(f);

        OutputStream os = new FileOutputStream("copy_" + f.getName());

        byte[] cache = new byte[64];

        for (; true;) {
            int n = is.read(cache);
            if (n == -1) {
                break;
            }
            // 写入到另一个新文件中
            os.write(cache, 0, n);
        }
        System.out.println("复制完成");
    }

}