I am new to this concept, i know the property of interface and abstract.
when i explain the concept to my friends, they asked me to create abstract class inside the interface.
please tell me , is it possible to create abstract class inside the interface.
i googled, but i am not able find the exact answer for my question.
i tried the below code ,but i dont know how to cal the AbstractMethod.
interface Student {
public abstract class Subject {
public void AbstractMethod(){
System.out.println("hi");
}
}
}
class Data implements Student {
public void ClassMethod() {
System.out.println("method 2");
}
}
public class NewClass {
public static void main(String[] args) {
Data s=new Data();
Student.Subject obj=new Student.Subject();// compiler error
s.ClassMethod();
}
}
Wouldn't something like this be better?
interface Student {
public abstract void sayHi();
}
class Data implements Student {
#Override
public void sayHi() {
System.out.println("method 2");
}
}
Yes, you can. Here in the below example, I used Anonymous Class but you can use Lambda Expression also
interface Student {
public abstract class Subject {
public abstract void AbstractMethod();
public void show(){
System.out.println("Show Method");
}
}
}
class Data implements Student {
public void ClassMethod() {
System.out.println("method 2");
}
}
public class NewClass {
public static void main(String[] args) {
Data s=new Data();
Student.Subject obj=new Student.Subject(){
public void AbstractMethod(){
System.out.println("hi");
}
};
obj.show();
obj.AbstractMethod();
s.ClassMethod();
}
}
Related
interface Y {
void search(String name);
}
class A implements Y {
void search(String name) {
//Is it possible to say: "If I was called from class B then do a search("B");
}
}
class B extends A {
}
public class Main {
public static void main(String[] args) {
B b = new B();
b.search();
}
}
Given the above code is it possible to reason in superclass which subclass was used for calling a method?
The reason I want to do this is because the code in Search is very similar for all Subclasses, the only thing that changes is the Classname, so I thought there is no need to Override in each subclass. I have updated the code to reflect this. Please let me know if there is a better way of doing it/
Calling this.getClass() inside your search method will give you the concrete class of the current instance.
For example:
class Example
{
static class A {
public void search() {
System.out.println(getClass());
}
}
static class B extends A {}
public static void main (String[] args) throws java.lang.Exception
{
new A().search();
new B().search();
}
}
outputs
class Example$A
class Example$B
The cleanest way to do it is to override the method in each subclass.
interface Y {
void search();
}
class A implements Y {
public void search(){
search("A");
}
protected void search(String name) {
// implement your searching algoithm here
}
}
class B extends A {
public void search(){
search("B");
}
}
public class Main {
public static void main(String[] args) {
B b = new B();
b.search();
}
}
That's the way inheritance is suppose to works. A super class should not know its subclasses.
And, in case you extends your class B, you can easily either:
-Keep the same behaviour as B:
class C extends B {
// do nothing, when calling search, it calls the method implemented in B
}
-Change the behaviour to search for "C"
class C extends B {
public void search(){
search("C"); // or search("whateveryouwant")
}
}
You can simply override the method in class B.
The other way could be to write the search() method as
void search() {
if (this.getClass().equals(B.class)) {
//The logic for B
} else if (this.getClass().equals(A.class)) {
//The logic for A
}
}
You have to provide the fully qualified name for the class.
Better follow template pattern.
interface Y {
void search(String name);
}
abstract class AbstractionTemplate implements Y{
#Override
public void search(String name) {
//a lot of code.
System.out.println("common stuff start");
doImplspecificStuffOnly();
System.out.println("common stuff end");
//a lot of code.
}
abstract void doImplspecificStuffOnly();
}
class A extends AbstractionTemplate{
#Override
void doImplspecificStuffOnly() {
System.out.println("a's stuff");
}
}
class B extends A {
#Override
void doImplspecificStuffOnly() {
System.out.println("B's stuff");
}
}
public class Main {
public static void main(String[] args) {
B b = new B();
b.search("hey");
}
}
Can Someone tell me with an example why an class should be defined inside an interface.
The below is the simple code i was trying.
interface Watsapp
{
class A
{
public void Validate()
{
}
};
abstract public void SendText();
public void SendPic();
};
its totally depends on logic requirements.
whenever we declare inner class, it treats as a data member so here also you can treat this class as a data member
just assume scenario some one needs object of A inside Interface and there is no class right now.
see eg.
public interface Watsapp
{
class A
{
public void Validate()
{
}
public String iDoSomething()
{
return "i did";
}
};
public A objOfA = new A();
abstract public void SendText();
public void SendPic();
};
And main Class is bellow:
public class TestMain {
public static void main(String[] str){
System.out.println( Watsapp.objOfA.iDoSomething());
}
}
mostly people create anonymous class for one time use, but here You created a class with name.
see:
public interface Watsapp
{
/*class A
{
public void Validate()
{
}
public String iDoSomething()
{
return "i did";
}
};*/
Thread t = new Thread()
{
public void run() {
// something ...
}
};
abstract public void SendText();
public void SendPic();
};
Thank you.
I need to write some importers. They need all the same initialization. So I try to write an abstract class, which does all the initialization and also has the main method, so that all sub-classes just need to implement run() to do their specific import work:
public abstract class AbstractImporter {
public AbstractImporter() {
// Initialization
}
public abstract void run();
public static void main(String[] args) {
AbstractImporter importer = new AbstractImporter();
importer.run();
}
}
public class ConcreteClass() {
public void run() {
// Do some importing
}
}
Of course it fails to create an instance of this abstract class (new AbstractImporter()).
Does anybody has any idea how to solve that? TIA!
Obviously you need a concrete class - anonymous or otherwise.
Better to move the main method to another class and instantiate the appropriate concrete class based on data (either your domain specific or a constant) and then run it. This way each implementation can be independent of other implementations.
public abstract class AbstractImporter {
public AbstractImporter() {
// Initialization
}
public abstract void run();
}
public class ConcreteImporter1 extends AbstractImporter {
public void run() {
//do something
}
}
public class ImporterMain() {
public static void main(String[] args) {
AbstractImporter importer = createImporter(args[1]);
importer.run();
}
private static AbstractImporter createImporter(String type) {
if (type.equals("1")) {
return new ConcreteImporter1();
}
....
}
}
new AbstracterImporter() {
public void run() {
// ...
}
};
I apologize for current lack of formatting, currently on a mobile device.
public abstract class AbstractImporter {
public AbstractImporter() {
// Initialization
}
public abstract void run();
public static void main(String[] args) {
AbstractImporter importer = new AbstractImporter(){
public void run() {
System.out.println("Anonymous implementation");
}
};
importer.run();
}
}
You cannot create an instance of an abstract class.
public abstract class AbstractImporter {
public AbstractImporter() {
// Initialization
}
public abstract void run();
}
public class ConcreteClass extends AbstractImporter{
public void run(){
//Implementation
}
public static void main(String args[]){
AbstractImporter ai = new ConcreteClass();
ai.run();
}
}
Having issue in Java,
we can call class methods like
interface samp{
public void printMsg();
}
ClassA implements samp{
public void printMsg()
{
S.o.p("Hi ClassA");
}
}
ClassB implements samp{
public void printMsg()
{
S.o.p("Hi ClassB");
}
}
public MainClass{
public static void main(String args())
{
samp s= new ClassA();
s.printMsg();
samp s= new ClassB();
s.printMsg();
}
}
we can do this, am having different type of class method not similar methods for all classes but I want to implement the future is it possible to do? is any other pattern for this, pls help me to find this.
like
ClassA{
public void fun1(){..}
public void fun2(){..}
}
ClassB{
public void fun3(){..}
public void fun4(){..}
}
want to call these methods using a single refrence, need to asign object to that refrence dynamically is it possible friends?...
Thanks in advance
You cant do that using common interface.You can only call the method which is defined in interface using an interface reference type, even though the object it points to belong to another class have different other methods.
you can call only those class function which are defined in interface because its reference can access only those functions. ex:
interface samp{
public void printMsg();
}
ClassA implements samp{
public void printMsg()
{
S.o.p("Hi ClassA");
}
public void newmthd(){
S.o.p("you can't call me from samp reference.");
}
}
ClassB implements samp{
public void printMsg()
{
S.o.p("Hi ClassB");
}
}
public MainClass{
public static void main(String args())
{
samp s= new ClassA();
s.printMsg();
s.newmthd() //error... s don't have any knowledge of this function.
samp s= new ClassB();
s.printMsg();
}
}
Define all the methods you want your reference to have in an a superclass, but leave the implementations empty. Then, create your subclass and override the necessary methods.
Example:
Class MySuperClass {
public void fun1() {}
public void fun2() {}
public void fun3() {}
public void fun4() {}
}
Class ClassA extends MySuperClass {
public void fun1() { //implementation details }
public void fun2() { //implementation details }
}
Class ClassB extends MySuperClass {
public void fun3() { //implementation details }
public void fun4() { //implementation details }
}
public Class Tester {
public static void main(String[] args) {
MySuperClass class1 = new ClassA();
MySuperClass class2 = new ClassB();
}
}
Here is a Java question
How can I implement the inner class's interface in outer class?
I try the following, but in vain. Thank You
class A implements interface B.C{
static class B{
interface C{
}
}
}
I would do like this :
Assuming both the classes are in same package with proper imports.
public class Nestedinterface {
public interface NestI{
void show();
}
}
public class NestedinterfaceImpl implements NestI {
public static void main(String a[]) {
NestI n = new NestedinterfaceImpl();
n.show();
}
public void show() {
// TODO Auto-generated method stub
System.out.println("Hello world");
}
}