写写java学习过程中_循环、判断

简单两个案例

1、循环案例：1+...+100=5050

2、判断案例：买电脑，余额大于5000买mac，余额小于5000大于200买dell，余额小于2000，别闹了。

 循环案例

package test;

public class First1{
    int a = 100;
    int b = 1;
    int sum = 0;
    void Sum(){
        while (b<=a){
            sum = sum + b ;
            b = b + 1 ;            
        }
        System.out.println("sum= " + sum);
    }    
public static void main(String []args){
    First1 Sum1 = new First1();
    Sum1.Sum();    
}
}

判断案例：

package test;
import java.util.Scanner;
public class First1{
    int a = 5000;
    int b = 2000;
    int money ;
    String computer;
//input为一个输入后字符串存储到m中然后转换为money存储在整型money中的方法
    void input(){
        Scanner s = new Scanner(System.in);
               String m = null;
               System.out.println("请输入您的钱：");
               m = s.next();
               money = Integer.parseInt(m);
    }
//buy为判断方法
    void buy(){
        if (money > a){
            computer = "mac";
        }
        else if (money < b){
            computer = "nothing";
        }
        else if(money > b && money < a ){
            computer = "dell";
        }
        System.out.println("you can buy " + computer +" ! ");
    }    
public static void main(String []args){
    First1 buy1 = new First1();
    buy1.input();
    buy1.buy();    
}
}

如果把money的这个全局变量变成方法buy1.buy的局部参数变量会怎样？

 

package test;
import java.util.Scanner;
public class First1{
    int a = 5000;
    int b = 2000;
    static int money ;
    String computer;
    void buy(int mon){
        if (mon > a){
            computer = "mac";
        }
        else if (mon < b){
            computer = "nothing";
        }
        else if(mon > b && mon < a ){
            computer = "dell";
        }
        System.out.println("you can buy " + computer +" ! ");
    }    
public static void main(String []args){
    //输入实际不用写成一个类的方法，直接写出到主函数，将输入的变量money直接通过对象传到方法内的参数mon即可
    First1 buy1 = new First1();
    Scanner s = new Scanner(System.in);
    String m = null;
    System.out.println("请输入您的钱：");
    m = s.next();
    money = Integer.parseInt(m);
    
    buy1.buy(money);
}
}