Java入门学习笔记（二）if语句for循环之类的

package practice;

public class practiceonly {
	public static void main(String[] args) {
		System.out.println(25/10);//取十位包含几个10
		System.out.println(25%10);//取各位
		
		int x=59 ;
		System.out.println(x/10);
		System.out.println(x%10);
		
		int y=11259;
		System.out.println(y/10000);//取第一位
		System.out.println(y%10000/1000);//取1259-》1
		System.out.println(y%1000/100);//直接取259-》2
		System.out.println(y%100/10);//取59，取到不能/100的那一位，再取十位
		System.out.println(y%10);//直接取各位
		
		
		System.out.println("我是一个无情的分界线");
		int a = 1;
		System.out.println(a++);//输出1，先输出a的值，再+1
		System.out.println(a);//输出2，a的值已经变为2
		a=1;
		System.out.println(++a);//输出2，先计算+1，再输出a的值
		System.out.println(a);//输出2
		
		int c = 1;
		System.out.println(--c);//0，符号在前，先自减，再打印
		System.out.println(--c-c-c--);//-1-(-1)-(-1)=1
		System.out.println(c);//-2	
	}
}

         *  x/10--取十位，几个10
         *  x/100-取百位，几个100
         *  x/1000-取千位，几个1000
         *  
         *  x%10--取各位，取到不能/10的位数
         *  x%100-取最后两位，取到不能/100的位数
         *  x%1000-取最后三位，取到不能/1000的位数
         *  x%10000-取最后四位，取到不能/10000的位数

package practice;

import java.util.Scanner;


public class practiceFindMax {
	public static void main(String[] args) {
		System.out.println("input the first number:");
		int a= new Scanner(System.in).nextInt();
		
		System.out.println("input the second number:");
		int b= new Scanner(System.in).nextInt();
		
		int max = a>b ? a : b ;
		System.out.println("the max number of two is "+max);
		
		
		
		int max = a>b ? (a>c?a:c) : (b>c?b:c)//判断三个值 先比较ab 再 ac bc
	}
}

package practice;

import java.util.Scanner;


public class judgeYear {
	public static void main(String[] args) {
		System.out.println("please inout the year you want to judge:");
		int year = new Scanner(System.in).nextInt() ;
		
		if((year%4==0 && year%100!=0)||year%400==0) {
			System.out.println(year+"年是闰年");
		}else {
			System.out.println(year+"年不是闰年");
		}		
	}

}

package practice;

import java.util.Scanner;

public class PractiseDiscount {
	public static void main(String[] args) {
		System.out.println("input how much money you've spent:");
		double money= new Scanner(System.in).nextDouble();
		
		if (money>=5000) {
			money=money*0.5;
		}else if (money>=2000) {
			money=money*0.8;
		}else if (money>=1000) {
			money=money*0.9;
		}
//		if (money>=1000 && money<2000) {
//			money = money*0.9;
//		}else if (money>=2000&&money<5000) {
//			money=money*0.8;
//		}else if(money>=5000) {
//			money=money*0.5;
//		}
		System.out.print("the total money is:"+money);
	}
}

package practice;

import java.util.Scanner;

public class PractiseScore {
	public static void main(String[] args) {
		System.out.println("input the score:");
		int score = new Scanner(System.in).nextInt();
		
		if (score<0||score>100) {
			System.out.println("please input the right score");
		}else if(score>=90) {
			System.out.println("优秀");
		}else if (score>=80) {
			System.out.println("良好");
		}else if (score>=70) {
			System.out.println("中等");
		}else if(score>=60) {
			System.out.println("及格");
		}else if (score<60) {
			System.out.println("不及格");
		}
	}
}

package practice;

import java.util.Scanner;

public class practiceswi {
	public static void main(String[] args) {
		System.out.println("input the number:");
		int n= new Scanner(System.in).nextInt();
		
		switch(n) {
			case 1: System.out.println("1");
			break;
			case 2: System.out.println("2");
			break;
			default: System.out.println("wrong");
		}
	}
}

package practice;

public class forloopnumbercount {
	public static void main(String[] args) {
		int i,sum=0,count=0;
		//1+。。。+100
		for(i=1;i<101;i++) {
			sum=sum+i;
		}
		System.out.println(sum);
		//100以内偶数之和
		sum=0;
		for(i=1;i<101;i++) {
			if(i%2==0) {
				sum=sum+i;
				count++;
			}
		}
		System.out.println(sum);
		System.out.println("count="+count);
	    //100奇数之和
			sum=0;
			for(i=1;i<101;i++) {
				if(i%2 !=0) {
					sum=sum+i;
				}
			}
			System.out.println(sum);	
		}
}

package practice2;

public class PractiseVariable {
	static String name;//默认为null 下面全是0 
	static byte b;
	static short c;
	static int d;
	static long e;
	static float f;
	static double g;
	static char h;
	static boolean i;//默认值为false
	public static void main(String[] args) {
		int abc;
		System.out.println(name);
		System.out.println(b);
		System.out.println(c);
		System.out.println(d);
		System.out.println(e);
		System.out.println(f);
		System.out.println(g);
		System.out.println(h);
		System.out.println(i);

	}
	
}

package practice2;

public class PractiseVari2 {
	static int count;
	static int sum=200;
	public static void main(String[] agrs) {
		int sum=100;
		System.out.println(sum);
		System.out.println(count);//0
		
		for (int i = 0; i < 10; i++) {//在for循环里定义所以只能在forloop里使用
            System.out.println(i);
		}
	}
}