Java字符流 #

public abstract class Reader {
    int read();                    // 读取一个字符
    int read(char[] cbuf);         // 读取到字符数组
    int read(char[] cbuf, int off, int len);  // 读取指定范围
    long skip(long n);             // 跳过n个字符
    boolean ready();               // 是否可读
    void close();                  // 关闭流
}

try (FileReader fr = new FileReader("test.txt")) {
    // 读取单个字符
    int ch;
    while ((ch = fr.read()) != -1) {
        System.out.print((char) ch);
    }
    
    // 读取到字符数组
    char[] buffer = new char[1024];
    int len;
    while ((len = fr.read(buffer)) != -1) {
        System.out.println(new String(buffer, 0, len));
    }
}

try (BufferedReader br = new BufferedReader(new FileReader("test.txt"))) {
    // 按行读取
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
}

try (InputStreamReader isr = new InputStreamReader(
        new FileInputStream("test.txt"), "UTF-8")) {
    char[] buffer = new char[1024];
    int len;
    while ((len = isr.read(buffer)) != -1) {
        System.out.println(new String(buffer, 0, len));
    }
}

public abstract class Writer {
    void write(int c);             // 写入一个字符
    void write(char[] cbuf);       // 写入字符数组
    void write(char[] cbuf, int off, int len);  // 写入指定范围
    void write(String str);        // 写入字符串
    void write(String str, int off, int len);   // 写入字符串指定范围
    Writer append(CharSequence csq);  // 追加
    void flush();                  // 刷新缓冲区
    void close();                  // 关闭流
}

try (FileWriter fw = new FileWriter("output.txt")) {
    fw.write("Hello World");
    fw.write("\n");
    fw.write("你好世界");
    fw.flush();
}

// 追加模式
try (FileWriter fw = new FileWriter("output.txt", true)) {
    fw.write("追加内容\n");
}

try (BufferedWriter bw = new BufferedWriter(new FileWriter("output.txt"))) {
    bw.write("第一行");
    bw.newLine();  // 换行
    bw.write("第二行");
    bw.flush();
}

try (OutputStreamWriter osw = new OutputStreamWriter(
        new FileOutputStream("output.txt"), "UTF-8")) {
    osw.write("Hello World");
    osw.flush();
}

public static String readFile(String path) throws IOException {
    StringBuilder sb = new StringBuilder();
    try (BufferedReader br = new BufferedReader(new FileReader(path))) {
        String line;
        while ((line = br.readLine()) != null) {
            sb.append(line).append("\n");
        }
    }
    return sb.toString();
}

public static void writeFile(String path, String content) throws IOException {
    try (BufferedWriter bw = new BufferedWriter(new FileWriter(path))) {
        bw.write(content);
        bw.flush();
    }
}

public static void copyTextFile(String src, String dest) throws IOException {
    try (BufferedReader br = new BufferedReader(new FileReader(src));
         BufferedWriter bw = new BufferedWriter(new FileWriter(dest))) {
        String line;
        while ((line = br.readLine()) != null) {
            bw.write(line);
            bw.newLine();
        }
    }
}

try (PrintWriter pw = new PrintWriter(new FileWriter("output.txt"))) {
    pw.println("第一行");
    pw.println("第二行");
    pw.printf("格式化: %d, %.2f%n", 100, 3.14159);
}

PrintWriter pw = new PrintWriter(System.out, true);
pw.println("Hello");

String text = "Hello World";
try (StringReader sr = new StringReader(text)) {
    int ch;
    while ((ch = sr.read()) != -1) {
        System.out.print((char) ch);
    }
}

try (StringWriter sw = new StringWriter()) {
    sw.write("Hello");
    sw.write(" World");
    System.out.println(sw.toString());  // Hello World
}