Interview
Question Answer for Java Developer
How to
create a singleton class in Java?
Singleton class creates only one instance in entire
application and program.
It means that we can’t create multiple instance of Singleton
class. Let’s See sample output of below
program:
testSingleton_obj:
mvc.model.TestSingleton@7852e922
testSingleton_obj1:
mvc.model.TestSingleton@7852e922
Here, you are seeing same object while using to print object
of class,
System.out.println(testSingleton);
System.out.println(testSingleton1);
This will print object. In the below program we have created
to object as
TestSingleton testSingleton_obj = getInstance();
TestSingleton testSingleton_obj1 = getInstance();
Program code:
public class TestSingleton {
private static TestSingleton TestObj;
static{
TestObj = new TestSingleton();
}
private TestSingleton(){
}
public static TestSingleton
getInstance(){
return TestObj;
}
public static void main(String a[]){
TestSingleton testSingleton_obj = getInstance();
System.out.println("testSingleton_obj:
"+testSingleton_obj);
TestSingleton testSingleton_obj1 = getInstance();
System.out.println("testSingleton_obj1:
"+testSingleton_obj1);
}
}
Console
output:
testSingleton_obj:
mvc.model.TestSingleton@7852e922
testSingleton_obj1:
mvc.model.TestSingleton@7852e922