在处理必须关闭的资源时，始终要先考虑用try-with-resources。因为finally块中的代码可能也会抛出异常，后一个异常会完全抹除第一个异常，堆栈中不会记录第一个异常。如果改用try-with-resources，后面的异常会被终止，以保留第一个异常。

//范例1

static String firstLineOfFile(String path) throws IOException{
	try(**BufferedReader br = new BufferedReader(new FileReader(path))**){
		return br.readLine();
}

}

//范例2

static void copy(String src,String dst) throws IOException{
	try(**InputStream   in = new FileInputStream(src);
		OutputStream out = new FileOutputStream(dst)**)
	){
		byte[] buf = new byte[BUFFER_SIZE];
		int n;
		while((n = in.read(buf) >= 0))
			out.write(buf,0,n);
}

}

//范例3

static String firstLineOfFile(String path，String defaultVal) {
	try(**BufferedReader br = new BufferedReader(new 				  FileReader(path))**){
		return br.readLine();
}catch(IOException  e){
	return defaultVal;
}

}