Java grammar basic exercises-22 days study notes

package com.xin;
import com.xin.base.Practice;
import com.xin.base.*;
import java.util.Scanner;


public class Applicant
{
		public static void main (String[] args){
				
			  new Practice().ToCompare();
				
				 new Practice1().add();
					
					new Practice2().change();
					
					new Practice3().shiLiu();
					
	  }
	  
	  package com.xin.base;

public class Practice
{
		public void ToCompare (){
				
					//三个数比较最大值
			
					int num1 = 10;
				
		
					int num2 = 70;
				
			
					int num3 = 30;
				
			
					int max = (num1 > num2 ) ?num1 : num2;
				
				
					int max2 = (max > num3) ? max : num3;
				
			
					System.out.println("这三个数的最大数为:"+max2);
				
		}
}

package com.xin.base;

public class Practice1
{
		public void add(){
				
				
				//编写程序，声明两个double型变量并且赋值，判断第一个数大于10.0且第二个数小于20.0
				
				//打印两数之和，否则打印两数乘积，
				
				double a1 = 15.2;
				
				
				double a2 = 34.2;
				
				
				double a3 = (a1 > 10 && a2 < 20) ? (a1+a2) : (a1*a2);
		
			
				System.out.println(a3);
		}
}

package com.xin.base;

public class Practice2
{
		//交换两个值，定义一个中间变量
		public void change(){
				
		int a = 5;
		System.out.println(a);
		
		int b = 55;
		System.out.println(b);
		
		int c = 0;
		
	  	c = a; //把a的值赋值给c，a就为0
				
				a = b; //把b给a b为0
				
				b = c; //最后把c的值给b完成交换
				
				System.out.println("交换后a的值为"+a);
				
				System.out.println("交换后b的值为"+b);
				
		}
}

package com.xin.base;


public class Practice3
{
		public void shiLiu (){
				//把一个数转换为16进制
				//60
				int i = 75;
				//位运算  与15 也就是1111
				int j = i&15;
				//取出来了最后4个为一组的二进制 16禁止0-9  a，b，c，d，e
				//此处判断是否是9以上的数字，通过char A对应的编码是97 +1就是b，+2就是c
				String sum = (j > 9) ? (char)( j - 10 + 'A') + "": j+ "" ;
				//在取第二位的数，先将它又移4位
				int k = i >>> 4;
				String sum1 = (k > 9) ?(char)(k - 10+ 'A') + "" : k + "";
				
				System.out.println(sum1+""+sum);
				 
				
		}
}

package com.xin.base;
import java.util.Scanner;

public class Practice4
{
		//if  else结构
	
	public void change1 ( ){
	int num = 90;
	
	if (num == 100){
			System.out.println("奖励一个嘿嘿嘿");
	}else if(num <= 80 && num >= 60){
			System.out.println("奖励一个么么哒");
	}else {
			System.out.println("拜拜");
	}
		
	}
		
}