public class Test {
    static boolean bool;
    static byte by;
    static char ch;
    static double d;
    static float f;
    static int i;
    static long l;
    static short sh;
    static String str;
 
    public static void main(String[] args) {
        System.out.println("Bool :" + bool);
        System.out.println("Byte :" + by);
        System.out.println("Character:" + ch);
        System.out.println("Double :" + d);
        System.out.println("Float :" + f);
        System.out.println("Integer :" + i);
        System.out.println("Long :" + l);
        System.out.println("Short :" + sh);
        System.out.println("String :" + str);
    }
}

　　结果：

Bool     :false
Byte     :0
Character:
Double   :0.0
Float    :0.0
Integer  :0
Long     :0
Short    :0
String   :null