Java文件读写操作

对文件内容按字符读取

public class WriteRead1 {
    public static void main(String[] args) throws IOException {
        write1();
        read1();
    }

    private static void read1() throws IOException {
        File file = new File("c:/temp/a.txt");
        FileReader fr = new FileReader(file);
        char[] ch = new char[100];
        fr.read(ch);
        for (char c:ch){
            System.out.println(c);
        }
    }

    private static void write1() throws IOException {
        File file = new File("c:/temp/a.txt");
        //如果文件不存在则进行新建文件
        if (!file.exists()){
            file.createNewFile();
        }
        FileWriter fw = new FileWriter(file);
        fw.write("Hello world");
        fw.flush();
        fw.close();
    }

}

对文件内容进行整行读取

public class WriteRead2 {
    public static void main(String[] args) throws IOException {
        write2();
        read2();
    }

    private static void read2() throws IOException {
        File file = new File("c:/temp/a.txt");
        BufferedReader br = new BufferedReader(new FileReader(file));
        String line;
        while((line = br.readLine()) != null){
            System.out.println(line);
        }
        br.close();
    }

    private static void write2() throws IOException {
        File file = new File("c:/temp/a.txt");
        //如果文件不存在则新建文件
        if (!file.exists()){
            file.createNewFile();
        }
        BufferedWriter bw = new BufferedWriter(new FileWriter(file));
        bw.write("Hello world");
        bw.newline();
        bw.flush();
        bw.close();
    }
}

以字节的形式写入文件，读取文件时先读取字节数组，再将字节数组转换为字符串形式

public class WriteRead3 {
    public static void main(String[] args) throws IOException {
        write3();
        read3();
    }

    private static void read3() throws IOException {
        File file = new File("c:/temp/a.txt");
        FileInputStream fis = new FileInputStream(file);
        byte[] bys = new byte[100];
        while (fis.read(bys, 0, bys.length) != -1) {
            System.out.println(new String(bys));
        }
        fis.close();
    }

    private static void write3() throws IOException {
        File file = new File("c:/temp/a.txt");
        //如果文件不存在则新建文件
        if (!file.exists()) {
            file.createNewFile();
        }
        FileOutputStream fos = new FileOutputStream(file);
        fos.write("Hello world".getBytes());
        fos.close();
    }
}