frog.java

JAVA编程思想第四版英文原版习题答案. pdf原版的

// reusing/Frog.java
// TIJ4, Chapter Reusing, Exercise 16, page 262
/* Create a class called Amphibian. From this, inherit a class called Frog. 
* Put appropriate methods in the base class. In main(), create a Frog and upcast
* it to Amphibian, and demonstrate that all the methods still work.
*/
import static org.greggordon.tools.Print.*;

class Amphibian {
	protected void swim() {
		println("Amphibian swim");		
	}
	protected void speak() {
		println("Amphibian speak");
	}
	void eat() {
		println("Amphibian eat");
	}
	static void grow(Amphibian a) {
		println("Amphibian grow");
		a.eat();
	}
}

public class Frog extends Amphibian {
	public static void main(String[] args) {
		Frog f = new Frog();
		// call base-class methods:
		f.swim();
		f.speak();
		f.eat();
		// upcast Frog to Amphibian argument:
		Amphibian.grow(f);
	}
}