public class Demon02 {
    public static void main(String[] args) {
        /*String a="hello";
        int num=20;
        System.out.println(a);
        System.out.println(num);*/
        int mum1 =10;  //常用
        byte num2=20;
        short mum4=30;
        long num3=30L;     //在数字后面加个L
        float mun5=50.1F;   //在数字后面加个F
        double num6=3.1415926;

        System.out.println(num2);

        char name='中';

        String name1 ="张平";
        //布尔值
        boolean flag=true;