ex9(2).java

JAVA编程思想第四版英文原版习题答案. pdf原版的

// typeinfo/Ex9.java
// TIJ4 Chapter Typeinfo, Exercise 9, page 562
// Modify the previous exercise so that it uses Class.getDeclaredFields() 
// to also display information about the fields in a class.

class A { int i; String s; }

class B extends A { int j; float f; }

class C extends B { int k; B b;}

public class Ex9 {
	public static void Hierarchy(Object o) {
		Object[] fields = o.getClass().getDeclaredFields();
		if(fields.length == 0)
			System.out.println(o.getClass() + " has no fields");
		if(fields.length > 0) {
			System.out.println("Field(s) of " + o.getClass() + ":");
			for(Object obj : fields) 
				System.out.println(" " + obj);
		}
		if(o.getClass().getSuperclass() != null) {			
			System.out.println(o.getClass() + " is a subclass of " + 
				o.getClass().getSuperclass()); 
			try {
				Hierarchy(o.getClass().getSuperclass().newInstance());
			} catch(InstantiationException e) {
				System.out.println("Unabloe to instantiate obj");
			} catch(IllegalAccessException e) {
				System.out.println("Unable to access");
			}
		} 
	}		
	public static void main(String[] args) {
		Hierarchy(new C());
	}
}