// 根据Key读取Value

public String getValueByKey(String filePath, String key) {

Properties pps = new Properties();

try {

InputStream in = new BufferedInputStream(new 

FileInputStream(filePath));

pps.load(in);

String value = pps.getProperty(key);

// System.out.println(key + " = " + value);

return value;

} catch (IOException e) {

e.printStackTrace();

return null;

}

}

public void writeProperties(String filePath, String key, String value)

 throws IOException {

Properties pps = new Properties();

InputStream in = new FileInputStream(filePath);

pps.load(in);

OutputStream out = new FileOutputStream(filePath);

pps.setProperty(key, value);

// 以适合使用 lad 方法加载到 Properties 表中的格式，

// 将此 Properties 表中的属性列表（键和元素对）写入输出流

pps.store(out, "Update " + key);

}

public static void main(String[] args) throws IOException {

// 通过获取JVM环境变量“user.dir”的方式定义文件的相对路径

// 后续的代码都会以此方式定义文件路径，便于代码在不同电脑上移植

String path = System.getProperty("user.dir") + "\\data\\";

PropReadWrite prw = new PropReadWrite();

String value = prw.getValueByKey(path + "Users.properties", "63.name");

System.out.println(value);

prw.getAllProperties(path + "Users.properties");

prw.writeProperties("Users.properties", "63.name", "chengdu");

}