王烊烊202302050115

w4/Circle.java

@@ -0,0 +1,10 @@
+package w4;
+public class Circle extends Shape{
+    private double R;
+    public Circle(double R){
+        this.R=R;
+    }
+    public double getArea(){
+        return Math.PI*R*R;
+    }
+}

w4/Rectangle.java

@@ -0,0 +1,12 @@
+package w4;
+public class Rectangle extends  Shape {
+    private double wide;
+    private double high;
+    public Rectangle(double wide,double high){
+        this.wide=wide;
+        this.high=high;
+    }
+    public double getArea(){
+        return wide*high;
+    }
+}

w4/Shape.java

@@ -0,0 +1,7 @@
+package w4;
+public abstract class Shape {
+    public abstract double getArea();
+}
+
+
+

w4/ShapeUtil.java

@@ -0,0 +1,6 @@
+package w4;
+public class ShapeUtil {
+    public static void printArea(Shape shape){
+        System.out.printf("图形面积:%.2f%n",shape.getArea());
+    }
+}

w4/Test.java

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+package  w4;
+public class Test {
+    public  static void main(String[] args){
+        Shape circle=new Circle(5);
+        Shape rectangle=new Rectangle(5,12);
+        Shape triangle=new Triangle(2,4);
+        ShapeUtil.printArea(circle);
+        ShapeUtil.printArea(rectangle);
+        ShapeUtil.printArea(triangle);
+    }
+}

w4/Triangle.java

@@ -0,0 +1,12 @@
+package w4;
+public class Triangle extends  Shape {
+    private double base;
+    private double high;
+    public Triangle(double base,double high){
+        this.base=base;
+        this.high=high;
+    }
+    public double getArea(){
+        return base*high*0.5;
+    }
+}