[Java知识库]使用java读取文件内容为字符串

public class Test {
    public static void main(String[] args) {
        // 方法1（保持文件原状）：
        File file = new File("C:\\download\\202104.json");
        Long filelength = file.length();
        byte[] filecontent = new byte[filelength.intValue()];
        try {
            FileInputStream in = new FileInputStream(file);
            in.read(filecontent);
            in.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        String fileStr1 = new String(filecontent);
        System.out.println(fileStr1);

        // 方法2（不会保持文件原状）：
        StringBuilder sb = new StringBuilder();
        try {
            BufferedReader reader = new BufferedReader(new FileReader("C:\\download\\202104.json"));
            String s = null;
            while ((s = reader.readLine()) != null) {
                sb.append(s);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        String fileStr2 = sb.toString();
        System.out.println(fileStr2);
    }
}