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Ans. By putting code within static method. With Java 6 and earlier versions, even static block can be used. | ||||
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Ans. A static initialization block is a normal block of code enclosed in braces, { }, and preceded by the static keyword. Here is an example: static { // whatever code is needed for initialization goes here } A class can have any number of static initialization blocks, and they can appear anywhere in the class body. The runtime system guarantees that static initialization blocks are called in the order that they appear in the source code. | ||||
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Ans. No. Static methods belong to the class and not the objects. They belong to the class and hence doesn't fit properly for the polymorphic behavior. A static method is not associated with any instance of a class so the concept of overriding for runtime polymorphism using static methods is not applicable. | ||||
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Ans. Yes.we cannot access them directly but we can access them using object reference.Static methods belong to a class and not objects whereas non static members are tied to an instance. Accessing instance variables without the instance handler would mean an ambiguity regarding which instance the method is referring to and hence its prohibited. | ||||
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Ans. By static import , we can access the static members of a class directly without prefixing it with the class name. | ||||
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Ans. We can do so through a static public member method or static block. | ||||
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Ans. Inner class is a type of nested class. Inner classes are non static nested classes i.e the one that are associated with the instance of outer class. | ||||
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Ans. static loading - Classes are statically loaded with Java new operator. dynamic class loading - Dynamic loading is a technique for programmatically invoking the functions of a class loader at run time. Class.forName (Test className); | ||||
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Ans. The accessibility (public, protected, etc.) of the static nested class is defined by the outer class. A static nested class is not an inner class, it's a top-level nested class. The name of the static nested class is expressed with OuterClassName.NestedClassName syntax. When you define an inner nested class (or interface) inside an interface, the nested class is declared implicitly public and static. Static nested classes can be declared abstract or final. Static nested classes can extend another class or it can be used as a base class. Static nested classes can have static members. Static nested classes can access the members of the outer class (only static members, obviously). The outer class can also access the members (even private members) of the nested class through an object of nested class. If you don't declare an instance of the nested class, the outer class cannot access nested class elements directly. | ||||
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Ans. Yes, it is possible by using a static block in the Java program. | ||||
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Ans. No. Even though "this" would mean a reference to current object id the method gets called using object reference but "this" would mean an ambiguity if the same static method gets called using Class name. | ||||
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Ans. Both belong to the class as a whole and not to the individual objects. Static methods are explicitly called for execution whereas Static block gets executed when the Class gets loaded by the JVM. | ||||
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Ans. Program throws "NoSuchMethodError" error at runtime . | ||||
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Ans. No the static block won't get executed as the referenced variable in the Test class is final. Compiler replaces the content of the final variable within Demo.main method and hence actually no reference to Test class is made. | ||||
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Ans. Yes. | ||||
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Ans. Yes. static method is not accessed by the instance of class. Either you call it by the class name or the reference. | ||||
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Ans. import static java.lang.System.*; | ||||
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Ans. It means that the type of variables are checked at compile time in Java.The main advantage here is that all kinds of checking can be done by the compiler and hence will reduce bugs. | ||||
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Ans. Yes, Effective Java 8. | ||||
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Ans. No, only using Interface Name. | ||||
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Ans. Yes , we can do that as static methods are not accessible using references and hence cannot lead to conflict. We cannot do inverse as Default methods cannot be overridden with the static methods in derived interface. | ||||
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Ans. Still No in case we are making use of inheritance. we may have problem wherein we have program flow moving across common inherited method and specific methods of the derived class. call made to another static method in the parent class will only access the static class of the Parent class irrespective of the call from any of the derived class. | ||||
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Ans. Static methods can be called using instance references wherein this would have made sense but static method can also be called using Class name wherein this would mean nothing and hence forbidden. | ||||
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Ans. Final makes sure that the value doesn't change after initialization and static makes sure that there is only one copy that can be shared across objects. Making it non static will unnecessarily create a different copy per object wherein the same value will kept for all copies ( as its final and cannot be changed ). | ||||
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Ans. Static block is like static method that gets executed upon class loading. The way static method allows accessing member variables ( using object references only ), the same static block can also access and initialize member variables. | ||||
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Ans. Advantages Can do meta object operations ( like validating something before creating objects , keep count of number of objects ) Can do operations which have nothing to do with objects but still you want them to be tied to Class. Disadvantages Commonly used to static variables sometime leads to problems due to access by different objects. Are not tied to objects so doesn't reflect pure Object Oriented approach. Needs to be synchronized so as to avoid update conflicts by mutiple objects and threads. Some limitation in testing as not all frameworks have facility to mock them. Powermock has but Mockito doesnt | ||||
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Ans. Static methods are resolved during compile time and hence they cannot participate in runtime polymorphism. Instance methods are resolved during runtime. | ||||
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Ans. Methods , Variables , Initialization Blocks and nested Classes | ||||
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Ans. Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables. | ||||
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Ans. Singleton class instance is initiated using new keyword whereas static class instance is created using static method. | ||||
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