This bytecode is not platform specific and can be executed on any computer. Basic Core Java Interview Questions: Q1. There are three built-in classloaders in Java. The constructor can be defined as the special type of method that is used to initialize the state of an object. Since the compile-time errors are better than runtime errors, Java renders compile-time error if you inherit 2 classes. Q34. Ans: JDK is development Kit of Java and is required for development only and to run a Java program on a machine, JDK isn't required. Answer: Here, we are initializing a string variable … I want my class to be developed in such a way that no other class (even derived class) can create its objects. Some of the important classes provided by Collection API include ArrayList, HashMap, TreeSet and TreeMap. Ans: If a class has multiple constructors, it's possible to call one constructor from the body of another one using this(). The types of access specifiers for classes are: 1. Method overloading is the polymorphism technique which allows us to create multiple methods with the same name but different signature. The following list contains 100 important Core Java interview questions for freshers as well as Java interview questions and answers for experienced programmers to help them prepare for the interview. Recommended Read => We have covered Core Java Interview Questions in earlier articles here. Because the object is not required to call the static method. In this list of Basic Java interview questions, we have covered all commonly asked basic and advanced Core Java interview questions with detailed answers to help you clear the job interview. Whenever we run the java program, it is loaded first by the classloader. String and StringBuffer both represent String objects. This blog on Java Interview Questions is categorized into three parts as mentioned below: 1. What's the significance of packages? What's the purpose of Static methods and static variables? The object cloning is used to create the exact copy of an object. 1. Can a class have multiple constructors? Can we call the constructor of a class more than once for an object? Q89. A sub-class is a class which inherits from another class called super class. There are five types of inheritance in Java. How garbage collection is done in Java? Consider the following example. Here, the data type of the variables a and b, i.e., byte gets promoted to int, and the first parameterized constructor with the two integer parameters is called. Q75. 3. We have compiled the most frequently asked Java Interview Questions and Answers that will help you prepare for the Basic Java interview questions that an interviewer might ask you during your interview. Public : Class,Method,Field is accessible from anywhere. An infinite loop can be broken by defining any breaking logic in the body of the statement blocks. The local variables are not initialized to any default value, neither primitives nor object references. Can we have any other return type than void for main method? It is used for runtime polymorphism and to implement the interface methods. Ans: If an exception is raised in Try block, control passes to catch block if it exists otherwise to finally block. C++ creates a new inheritance tree always. How infinite loop is declared? Give example. By writing a class that extend Java.Lang.Thread class. When an object contains the other object, if the contained object cannot exist without the existence of container object, then it is called composition. Q70. The best example of singleton usage scenario is when there is a limit of having only one connection to a database due to some driver limitations or because of any licensing issues. However, as we know that, it is unnecessary to access static variables through objects, therefore, it is not the best practice to use this to refer static members. Ans: Java provides a Collection API which provides many useful methods which can be applied on a set of objects. Ans: In multi-threading, access to the resources which are shared among multiple threads can be controlled by using the concept of synchronization. Ans: In java, float takes 4 bytes in memory while Double takes 8 bytes in memory. How it's possible? The core Java interview questions are categorized in Basics of Java interview questions, OOPs interview questions, String Handling interview questions, Multithreading interview questions, collection interview questions, JDBC interview questions, etc. If we don't implement Cloneable interface, clone() method generates CloneNotSupportedException. Java is an object-oriented computer language. For example in the class below we have two print methods with same name but different parameters. Previous Next In this post, we will some important interview questions specifically on Java 8. Ans: In java, each object when created gets a memory space from a heap. Ans: A thread in Java can be in either of the following states: Q59. 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. Ans: Round(3.7) returns 4 and Ceil(3.7) returns 4. There are the following features in Java Programming Language. Ans: No, we can neither cast any other primitive type to Boolean data type nor can cast Boolean data type to any other primitive data type. The Java code is compiled by JVM to be a Bytecode which is machine independent and close to the native code. Singleton class concept is useful for the situations when there is a need to limit the number of objects for a class. How can we pass argument to a function by reference instead of pass by value? Both classes are in the same package. Polymorphism (Extensibility ) is another great benefit which allow new functionality to be introduced without effecting existing derived classes. Q92. In Java, Object is an instance of the class having the instance variables as the state of the object and the methods as the behavior of the object. Java is used by approx 10 Million developers worldwide to develop applications for 15 Billion devices supporting Java. The output of the program is 0 because the variable i is initialized to 0 internally. … Ans: If there is a hierarchy of inheritance used, a class can be a super class for another class and a sub-class for another one at the same time. All objects of a class implementing serializable interface get serialized and their state is saved in byte stream. Q52. Ans: Key benefit of using inheritance is reusability of code as inheritance enables sub-classes to reuse the code of its super class. Database related code can be placed in a method which hs synchronized keyword so that only one thread can access it at a time. Q5. What's the difference between comparison done by equals method and == operator? The object of a class can be created by using the new keyword. It is invoked when the class is instantiated, and the memory is allocated for the object. It is used for Code Reusability and Method Overriding. Implements the real-time approach like inheritance, abstraction, etc. Q49. If we change any method to a final method, we can't override it. The first method accepts the integer and long type whereas the second method accepts long and the integer type.

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