只提交 W4 文件夹

W4/Area.java.txt

@@ -0,0 +1,42 @@
+abstract class Area{
+    public abstract double draw();
+}
+class circle extends Area{
+    double r;
+    public double draw() {
+        double area = 3.14 * r * r;
+        System.out.println(area);
+        return area;
+    }
+}
+class rectangle extends Area{
+    double l,b;
+    public double draw() {
+        double area = l * b;
+        System.out.println(area);
+        return area;
+    }
+}
+class tangle extends Area{
+    double b,h;
+    public double draw() {
+        double area = 0.5 * b * h;
+        System.out.println(area);
+        return area;
+    }
+}
+public class Main{
+    static void main(String[] args) {
+        circle c=new circle();
+        c.r=5;
+        c.draw();
+        rectangle a=new rectangle();
+        a.l=5;
+        a.b=4;
+        a.draw();
+        tangle t=new tangle();
+        t.b=5;
+        t.h=4;
+        t.draw();
+    }
+}