方法重载，向上转型

原则：匹配离它最近的类型
int -> int 
	-> long
	-> float
	-> double
	
(short)int -> short

public static void main(String[] args) {
	method(1);
	
	method((short)1);
}

public static void method(int a) {
	System.out.println("int: " + a);
}

public static void method(long a) {
	System.out.println("long: " + a);
}

public static void method(float a) {
	System.out.println("float: " + a);
}

public static void method(double a) {
	System.out.println("double: " + a);
}

public static void method(short a) {
	System.out.println("short: " + a);
}