I have a sample code to solve which is based on inner classes:
package inner;
class A {
void m() {
System.out.println("Outer");
}
}
public class TestInner {
public static void main(String[] args) {
new TestInner().go();
}
private void go() {
new A().m();
class A{
void m(){
System.out.println("Inner");
}
}
new A().m();
}
class A{
void m(){
System.out.println("Middle");
}
}
}
The output given by above sample code is:
Middle
Inner
And my question is, given that I dont want to use the package name to create an object, how can I print the output as:
Outer
Inner
Since using a package is so obviously the answer, I assume you are looking for something obtuse.
You can add an outer class and call that.
class B extends A { }
// in TestInner.go()
new B().m();
class A{
void m(){
System.out.println("Inner");
}
}
new A().m();
public class TestInner {
public static void main(String[] args) {
new TestInner().go();
}
private void go() {
new inner.A().m(); //will produce output "Outer"
class A{
void m(){
System.out.println("Inner");
}
}
new A().m(); //will produce output "Inner"
}
class A{
void m(){
System.out.println("Middle");
}
}
Related
I have two scenarios
Without Extending:
class A
{
public void print()
{
System.out.println("Class A");
}
}
class B
{
B()
{
A obj=new A();
obj.print();
}
}
public class Main
{
public static void main(String[] args) {
B obj=new B();
}
}
With inheritance:
class A
{
public void print()
{
System.out.println("Class A");
}
}
class B extends A
{
B()
{
A obj=new A();
obj.print();
}
}
public class Main
{
public static void main(String[] args) {
B obj=new B();
}
}
As both work as same then why do we need to extend another class?
And what is the key difference between both methods?
public interface Counter{
class Base1{
protected int count1;
public Base1(){
count1=0;
}
#Override
public void putCount(){
System.out.println(count1);
}
}
}
How to access putCount() in interface's class method and count1 variable?
Try this:
Counter.Base1 myBase1 = new Counter.Base1();
myBase1.putCount();
The concept is called inner class, if you want to find further information. As count1 is protected, you cannot access it from the outside.
We tried to understand your query & this is what we got.
Plz check it
public interface Counter{
class Base1{
protected static int count1;
public Pblm(){
count1=0;
}
public static void putCount(){
System.out.println(count1);
}
}
}
The example below show how to call method of class inside an interface.
interface Outer1 {
public abstract void show();
class Inner1 {
public void display() {
System.out.println("Hello 1");
}
}
}
public class Test extends Outer1.Inner1 {
public static void main(String args[]) {
Test t1 = new Test(); t1.display();
}
}
See more at: link
I have two nested classes inside a class with the outer class extending another class. The structure is something like this.
public class EXTENSION_CLASS
{
public int Get_Value()
{
return(100);
}
}
public class OUTER extends EXTENSION_CLASS
{
public static class NESTED1
{
public void Method1()
{
int value=0;
value=Get_Value();
System.out.println("Method1: "+value);
}
}
public static class NESTED2
{
NESTED1 Nested1_Instance=new NESTED1();
public void Method2()
{
Nested1_Instance.Method1();
}
}
public void run()
{
NESTED2 Nested2_Instance=new NESTED2();
Nested2_Instance.Method2();
}
public static void main (String[] args)
{
OUTER New_Class=new OUTER();
New_Class.run();
}
}
I'm expecting the output: "Method1: 100". But, am getting the output: "OUTER.java:16: error: non-static method Get_Value() cannot be referenced from a static context value=Get_Value();". How can i make this working?
Cheers !
Rajesh.
One approach would be to have an instance of NESTED1 in NESTED2. For example:
private static class NESTED2
{
private NESTED1 nested1;
public NESTED2 (NESTED1 nested1) {
this.nested1 = nested1;
}
public void Method2()
{
nested1.Method1();
}
}
private static class NESTED2
{
public void Method2(NESTED1 nested1Instance)
{
nested1Instance.Method1();
}
}
That should do it with your class structure. Instead, with a modification like so....
private static class NESTED1
{
public *statc* void Method1()
{
...
}
}
private static class NESTED2
{
public *static* void Method2()
{
NESTED1.Method1();
}
}
... you could get away with no creation of objects.
If you make the methods static, you don't need to instantiate(create) a class object to call them first.
interface A {
void show();
}
public class Static {
public static void main(String args[]) {
A a = new A(){
public void show(){
System.out.println("In anonymous Class");
A b =new A(){
public void show(){
System.out.println("In nested Anonymous Class");
}
};
}
};
//a.show();
}
}
If I want the to print "In nested Anonymous Class", what should I use instead of a.show()?
//EDITED LATER
Thanks guys But unfortunately mis-typed the code....I didn't mean anonymous class inside a method...but inside the class itself. Sorry for the mistake. Here is the corrected code
interface A {
void show();
}
public class Static {
public static void main(String args[]) {
A a = new A() {
public void show() {
System.out.println("In anonymous Class");
};
A b = new A() {
public void show() {
System.out.println("In nested Anonymous Class");
}
};
};
a.show();
}
}
Normally, it's not possible, since A is an interface and interfaces don't have fields. However, it is possible to access this field using reflection. It is a bit of hack though and I wouldn't suggest using this in the "real world"!
interface A {
void show();
}
public class Static {
public static void main(String args[]) throws IllegalArgumentException, IllegalAccessException, SecurityException, NoSuchFieldException {
A a = new A() {
public void show() {
System.out.println("In anonymous Class");
};
public A b = new A() {
public void show() {
System.out.println("In nested Anonymous Class");
}
};
};
// Get the anonymous Class object
Class<? extends A> anonymousClass = a.getClass();
// Get field "b"
Field fieldB = anonymousClass.getField("b");
// Get the value of b in instance a and cast it to A
A b = (A) fieldB.get(a);
// Show!
b.show();
}
}
Note: a better way might be to simply declare a getter on your interface for variable b.
make a call to b.show(); just after class declaration.
A b =new A(){
public void show(){
System.out.println("In nested Anonymous Class");
}
};
b.show();
There is nothing you should use instead of a.show(). That line should be where you put it, and uncommented. Additionally you need b.show() inside:
public static void main(String args[]) {
A a = new A(){
public void show(){
System.out.println("In anonymous Class");
A b =new A(){
public void show(){
System.out.println("In nested Anonymous Class");
}
};
b.show();
}
};
a.show();
}
package tt;
class Out {
class Inner {
void print() {
System.out.println("i anm inner1");
}
}
public void run() {
Inner in = new Inner();
in.print();
}
}
class Out2 extends Out{
class Inner{
void print() {
System.out.println("i anm inner2");
}
}
}
public class Test {
/**
* #param args
*/
public static void main(String[] args) {
new Out2().run(); // 打印 i anm inner2
}
}
This program prints out ("i anm inner1") now.
How can I make the program print("i anm inner2")?
Instead of covering the inner class you could cover (override) a factory method in the base class, you the Out2.Inner must extend the Out.Inner
class Out {
class Inner {
void print() {
System.out.println("i anm inner1");
}
}
public Inner createInner(){
return new Inner();
}
public void run() {
Inner in = createInner();
in.print();
}
}
class Out2 extends Out {
class Inner extends Out.Inner {
void print() {
System.out.println("i anm inner2");
}
}
public Out.Inner createInner(){
return new Inner();
}
}
Either call the print() of the child's inner class
new Out2().new Inner().print();
Or, override run() inside Out2
#Override
public void run() {
Inner in = new Inner();
in.print();
}
you should override run() in out2