创建类

 1 public class juxing {
 2 
 3     
 4     double length;
 5     double wide;
 6    
 7     public juxing(double length1,double wide1){
 8         
 9         this.length = length1;
10         this.wide = wide1;
11     }
12      public double getarea(){
13         
14       double s = length*wide;
15        return s;
16         
17     }
18    
19     
20 }

 1 public class Test {
 2 
 3     public static void main(String[] args) {
 4 
 5         
 6 
 7         Juxing j = new Juxing(3, 4);
 8 
 9         System.out.println("矩形的面积是：" + j.getarea());
10 
11     }
12 }