java ++前缀

public class Sample {

    public static void main(String[] args) {
        int num1 = , num2 = ;
        int num3 = , num4 = ;
        ++num1;
        System.out.println("now num1: " + num1);
        System.out.println("now num2: " + (++num2)); // first the num2 gets incremented
        System.out.println("now num3: " + (num3++));
        num4++;
        System.out.println("now num4: " + (num4));
    }
}

OUTPUT:
now num1:
now num2:
now num3:
now num4: 

demo2

public class Sample {

    public static void main(String[] args) {
        int num = ;
        System.out.println("now num: " + (num++)); // this is post increment
        System.out.println("now num: " + num);
    }
}

OUTPUT:
now num:
now num: