java讀取json文件與其他文件

一、讀取json文件

直接讀取文件，並轉化爲map

ObjectMapper objectMapper = new ObjectMapper(); 
try {
	Map map = objectMapper.readValue(new File(filePath), Map.class);
} catch (Exception e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
} 

二、讀取普通文件

使用FileInputStream效率最高！

下面是每次讀取1024個字節

public static String readFile(String filePath) {
    StringBuffer stringBuffer = new StringBuffer("");
    byte[] buffer = new byte[1024];
    int count = 0;
    File file = new File(filePath);
    try {
        InputStream inputStream = new FileInputStream(file);
        while (-1 != (count = inputStream.read(buffer))) {
            stringBuffer.append(new String(buffer, 0, count));
        }
        inputStream.close();
    } catch (IOException ex) {
        ex.printStackTrace();
    }

    return stringBuffer.toString();
}

下面是讀取所有字節

public static String readFile(String filePath) {
	String encoding = "UTF-8";
	File file = new File(filePath);
	Long filelength = file.length();
	byte[] filecontent = new byte[filelength.intValue()];
	try {
		FileInputStream in = new FileInputStream(file);
		in.read(filecontent);
		in.close();
	} catch (FileNotFoundException e) {
		e.printStackTrace();
	} catch (IOException e) {
		e.printStackTrace();
	}
	try {
		return new String(filecontent, encoding);
	} catch (UnsupportedEncodingException e) {
		System.err.println("The OS does not support " + encoding);
		e.printStackTrace();
		return null;
	}
}