JAVA INTERVIEW QUESTION AND ANSWERS PDF
Java Interview Questions And Answers Pdf Yes, We can execute any code, even before the main method. We are using a static block. 5) Difference between method overloading and method overriding in java? . .. 9. 6) Difference . Core java Interview questions on Coding Standards. In this guide we will discuss about different types of questions that can be used in a Java interview, in order for the employer to test your skills in Java and.
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Dear readers, these Java Interview Questions have been designed the subject and later they continue based on further discussion and what you answer −. I was getting a lot of emails and comments to create java interview questions and answers PDF eBook. It was hard and time taking, but finally, it's done. Basic Java Interview Questions and Answers for Freshers or Experienced Pdf. This interview section questions contains a brief introduction to the Java.
Array List does not define the increment size. Vector defines the increment size. Array List can only use Iterator for traversing an Array List. Except Hashtable, Vector is the only other class which uses both Enumeration and Iterator.
Features Stack Heap Memory Stack memory is used only by one thread of execution.
300 Core Java Interview Questions | Set 1
Heap memory is used by all the parts of the application. Objects stored in the heap are globally accessible. Memory management is based on generation associated to each object. Lifetime Exists until the end of execution of the thread.
Heap memory lives from the start till the end of application execution. Usage Stack memory only contains local primitive and reference variables to objects in heap space. In case you are facing any challenges with these java interview questions, please comment on your problems in the section below. An interface cannot provide any code at all,just the signature.
Top 50+ Core Java Interview Questions and Answers
There are three built-in classloaders in Java. Bootstrap ClassLoader: This is the first classloader which is the superclass of Extension classloader. It loads the rt. Extension ClassLoader: This is the child classloader of Bootstrap and parent classloader of System classloader.
It loads the class files from the classpath. By default, the classpath is set to the current directory. You can change the classpath using "-cp" or "-classpath" switch. It is also known as Application classloader. Yes, Java allows to save our java file by.
It is empty, but not null. The program compiles and runs correctly because the order of specifiers doesn't matter in Java. The local variables are not initialized to any default value, neither primitives nor object references. In Java, access specifiers are the keywords which are used to define the access scope of the method, class, or a variable.
In Java, there are four access specifiers given below. Public The classes, methods, or variables which are defined as public, can be accessed by any class or method. Protected Protected can be accessed by the class of the same package, or by the sub-class of this class, or within the same class. Default Default are accessible within the package only.
By default, all the classes, methods, and variables are of default scope.
Private The private class, methods, or variables defined as private can be accessed within the class only. The methods or variables defined as static are shared among all the objects of the class. The static is the part of the class and not of the object. The static variables are stored in the class area, and we do not need to create the object to access such variables. Therefore, static is used in the case, where we need to define variables or methods which are common to all the objects of the class.
For example, In the class simulating the collection of the students in a college, the name of the college is the common attribute to all the students. Therefore, the college name will be defined as static. There are various advantages of defining packages in Java. Packages avoid the name clashes. The Package provides easier access control.
We can also have the hidden classes that are not visible outside and used by the package. It is easier to locate the related classes. Now, their sum 30 is treated as the string and concatenated with the string Javatpoint. Therefore, the output will be 30Javatpoint. We can achieve method overloading in two ways. Method overloading increases the readability of the program. Method overloading is performed to figure out the program quickly.
In Java, method overloading is not possible by changing the return type of the program due to avoid the ambiguity. No, We cannot overload the methods by just applying the static keyword to them number of parameters and types are the same. By Type promotion is method overloading, we mean that one data type can be promoted to another implicitly if no exact matching is found. As displayed in the above diagram, the byte can be promoted to short, int, long, float or double.
The short datatype can be promoted to int, long, float or double. The char datatype can be promoted to int, long, float or double and so on. There are two methods defined with the same name, i.
The first method accepts the integer and long type whereas the second method accepts long and the integer type. We can not tell that which method will be called as there is no clear differentiation mentioned between integer literal and long literal. This is the case of ambiguity. Therefore, the compiler will throw an error.
If a subclass provides a specific implementation of a method that is already provided by its parent class, it is known as Method Overriding. It is used for runtime polymorphism and to implement the interface methods. It is because the static method is the part of the class, and it is bound with class whereas instance method is bound with the object, and static gets memory in class area, and instance gets memory in a heap.
No, we cannot override the private methods because the scope of private methods is limited to the class and we cannot access them outside of the class. Yes, we can change the scope of the overridden method in the subclass.
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However, we must notice that we cannot decrease the accessibility of the method. The following point must be taken care of while changing the accessibility of the method. Yes, we can modify the throws clause of the superclass method while overriding it in the subclass. However, there are some rules which are to be followed while overriding in case of exception handling.
The method is overloaded in class Base whereas it is derived in class Derived with the double type as the parameter. In the method call, the integer is passed. Yes, all functions in Java are virtual by default. Now, since java5, it is possible to override any method by changing the return type if the return type of the subclass overriding method is subclass type.
It is known as covariant return type. The covariant return type specifies that the return type may vary in the same direction as the subclass.
Output Derived method called The method of Base class, i. In Test class, the reference variable b of type Base class refers to the instance of the Derived class.
Here, Runtime polymorphism is achieved between class Base and Derived. At compile time, the presence of method baseMethod checked in Base class, If it presence then the program compiled otherwise the compiler error will be shown. In this case, baseMethod is present in Base class; therefore, it is compiled successfully. However, at runtime, It checks whether the baseMethod has been overridden by Derived class, if so then the Derived class method is called otherwise Base class method is called.
In this case, the Derived class overrides the baseMethod; therefore, the Derived class method is called. In Java, the final variable is used to restrict the user from updating it.
If we initialize the final variable, we can't change its value. In other words, we can say that the final variable once assigned to a value, can never be changed after that. The final variable which is not assigned to any value can only be assigned through the class constructor. If we change any method to a final method, we can't override it. A final variable, not initialized at the time of declaration, is known as the final blank variable.
We can't initialize the final blank variable directly. Instead, we have to initialize it by using the class constructor. It is useful in the case when the user has some data which must not be changed by others, for example, PAN Number. Consider the following example:. Yes, if it is not static, we can initialize it in the constructor.
If it is static blank final variable, it can be initialized only in the static block. Output 20 Explanation. Since i is the blank final variable. It can be initialized only once. We have initialized it to Therefore, 20 will be printed. Explanation The getDetails method is final; therefore it can not be overridden in the subclass. The constructor can never be declared as final because it is never inherited.
Constructors are not ordinary methods; therefore, there is no sense to declare constructors as final. However, if you try to do so, The compiler will throw an error.
No, we cannot declare an interface as final because the interface must be implemented by some class to provide its definition. Therefore, there is no sense to make an interface final.
However, if you try to do so, the compiler will show an error. The main difference between the final method and abstract method is that the abstract method cannot be final as we need to override them in the subclass to give its definition. JavaTpoint offers too many high quality services. Mail us on hr javatpoint. Please mail your requirement at hr javatpoint. Download Android App All Interview. I am good!! TestMethod ; System.
Person class constructor called Employee class constructor called. Method Overloading Interview Questions. Compile Time Error: Method Overriding Interview Questions. Next Topic Java interview Questions part 2. Javatpoint Services JavaTpoint offers too many high quality services. Java is mainly used for application programming. It is widely used in window, web-based, enterprise and mobile applications. It was an extension of C programming language.
Java was designed and created as an interpreter for printing systems but later extended as a support network computing.
It was designed with a goal of being easy to use and accessible to a broader audience. Java doesn't support multiple inheritance through class. It can be achieved by interfaces in java. Java supports pointer internally. However, you can't write the pointer program in java.The object of a class can be created by using the new keyword. There are two parameters required to add an element to HashMap object.
Thanks sir. What is class in Java? When it reaches the code t. JVM is the specification which must be implemented in the computer system. Javatpoint Services JavaTpoint offers too many high quality services.
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