第一种方法

private static void ReadFile(String filePath) {
    try {
        StringBuilder stringBuilder = new StringBuilder(50);
        FileReader fileReader = new FileReader(filePath);
        int i;
        while ( (i = fileReader.read()) != -1) {
            stringBuilder.append((char)i);
        }
        System.out.println(stringBuilder.toString());
    } catch (Exception e) {
        e.printStackTrace();
    }
}

第二种方法

private static void ReadFile(String filePath) {
    try {
        StringBuilder stringBuilder = new StringBuilder(50);
        FileReader fileReader = new FileReader(filePath);
        char[] bytes = new char[1024];
        while (fileReader.read(bytes) != -1) {
            stringBuilder.append(bytes);
        }
        System.out.println(stringBuilder.toString());
    } catch (Exception e) {
        e.printStackTrace();
    }
}

FileReader读取txt文件