從零自學JAVA-3.在程式中存儲和修改變數信息

1.創建變數；

2.使用不同類型的變數；

3.在變數中存儲值；

4.在數學表達式中使用變數；

5.把一個變數的值賦給另一個變數；

6.遞增/遞減變數的值。

程式Variable：使用不同類型的變數並賦初值

 1 package com.jsample;
 2 
 3 public class Variable {
 4     public static void main(String[] args){
 5         int tops;//無初值的整型變數
 6         float gpa;//無初值的單精度浮點型變數
 7         char key = 'C';//初值為‘C’的字元型變數
 8         String productName = "Larvets";//初值為“Larvets”的字元串型變數
 9     }//本程式無輸出
10 }

程式PlaneWeight：計算並輸出人在太陽系不同行星上的體重值

 1 package com.jsample;
 2 
 3 public class PlaneWeight {
 4     public static void main(String[] args){
 5         System.out.print("Your weight on Earth is ");
 6         double weight = 178;
 7         System.out.println(weight);//print()不會自動換行，println()會
 8 
 9         System.out.print("Your weight on Mercury is ");
10         double mercury = 178 * .378;
11         System.out.println(mercury);
12 
13         System.out.print("Your weight on Moon is ");
14         double moon = 178 * .166;
15         System.out.println(moon);
16 
17         System.out.print("Your weight on Jupiter is ");
18         double jupiter = 178 * 2.364;
19         System.out.println(jupiter);
20     }
21 }

程式PlaneWeightPlus：計算並輸出人在更多太陽系不同行星上的體重值

 1 package com.jsample;
 2 
 3 public class PlaneWeightPlus {
 4     public static void main(String[] args){
 5         System.out.print("Your weight on Earth is ");
 6         double weight = 178;
 7         System.out.println(weight);//print()不會自動換行，println()會
 8 
 9         System.out.print("Your weight on Mercury is ");
10         double mercury = weight * .378;
11         System.out.println(mercury);
12 
13         System.out.print("Your weight on Moon is ");
14         double moon = weight * .166;
15         System.out.println(moon);
16 
17         System.out.print("Your weight on Jupiter is ");
18         double jupiter = weight * 2.364;
19         System.out.println(jupiter);
20 
21         System.out.print("Your weight on Hesperus is ");
22         double hesperus = weight * .907;
23         System.out.println(hesperus);
24 
25         System.out.print("Your weight on Uranus is ");
26         double uranus = weight * .889;
27         System.out.println(uranus);
28     }
29 }

程式SquareSum：計算整型數x,y的平方和並輸出

1 package com.jsample;
2 
3 public class SquareSum {
4     public static void main(String[] args){
5         int x = 1;
6         int y = 1;
7         System.out.println(x * x + y * y);//輸出平方和
8     }
9 }