java古明源2024.9.27

EnumTest.java:

package gu;

public class EnumTest {

public static void main(String[] args) {

Size s=Size.SMALL;

Size t=Size.LARGE;

//s和t引用同一个对象？

System.out.println(s==t); //

//是原始数据类型吗？

System.out.println(s.getClass().isPrimitive());

//从字符串中转换

Size u=Size.valueOf("SMALL");

System.out.println(s==u); //true

//列出它的所有值

for(Size value:Size.values()){

System.out.println(value);

}

}

}

enum Size{SMALL,MEDIUM,LARGE};

TestDouble.java:

package gu;

public class TestDouble {

public static void main(String args[]) {

System.out.println("0.05 + 0.01 = " + (0.05 + 0.01));

System.out.println("1.0 - 0.42 = " + (1.0 - 0.42));

System.out.println("4.015 * 100 = " + (4.015 * 100));

System.out.println("123.3 / 100 = " + (123.3 / 100));

}

}

动手动脑：

package ming;

public class main {

public static void main(String[] args) {

// TODO Auto-generated method stub

int X=100;

int Y=200;

System.out.println("X+Y="+X+Y);

System.out.println(X+Y+"=X+Y");

}

}

四则运算

#include "stdafx.h"
#include<stdio.h>
#include<stdlib.h>
int main(int argc, char* argv[])
{
int i,j,k,sum;
for(int t = 0;t<30;t++)
{
printf("第%d道题：",t+1);
i = rand()%50;
j = rand()%50;
k = rand()%4;
switch(k)
{
case 0:
sum = i+j;
printf("%d+%d=%d\n",i,j,sum);
break;
case 1:
sum = i-j;
printf("%d-%d=%d\n",i,j,sum);
break;
case 2:
sum = i*j;
printf("%d*%d=%d\n",i,j,sum);
break;
case 3:
sum = i/j;
printf("%d/%d=%d\n",i,j,sum);
break;
default:
printf("出错！\n");
break;
}
}
return 0;

}