Dear readers, these Java Interview Questions have been designed especially to get you acquainted with the nature of questions you may encounter during your interview for the stop program java of Java Programming Language. What do you know about Java? Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.
What are the supported platforms by Java Programming Language? Linux like HP-Unix, Sun Solaris, Redhat Linux, Ubuntu, CentOS, etc. List any five features of Java? It’s compiler generates an architecture-neutral object file format, which makes the compiled code to be executable on many processors, with the presence of Java runtime system.
Java uses Just-In-Time compiler to enable high performance. Just-In-Time compiler is a program that turns Java bytecode, which is a program that contains instructions that must be interpreted into instructions that can be sent directly to the processor. It is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run-time. What is Java Virtual Machine and how it is considered in context of Java’s platform independent feature? When Java is compiled, it is not compiled into platform specific machine, rather into platform independent byte code. Some Java keywords are import, super, finally, etc.
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What do you mean by Object? Object is a runtime entity and it’s state is stored in fields and behavior is shown via methods. Methods operate on an object’s internal state and serve as the primary mechanism for object-to-object communication. A class is a blue print from which individual objects are created. A class can contain fields and methods to describe the behavior of an object. What kind of variables a class can consist of? A class consist of Local variable, instance variables and class variables.
Variables defined inside methods, constructors or blocks are called local variables. The variable will be declared and initialized within the method and it will be destroyed when the method has completed. Instance variables are variables within a class but outside any method. These variables are instantiated when the class is loaded. These are variables declared with in a class, outside any method, with the static keyword. Singleton class control object creation, limiting the number to one but allowing the flexibility to create more objects if the situation changes.
What do you mean by Constructor? Constructor gets invoked when a new object is created. If we do not explicitly write a constructor for a class the java compiler builds a default constructor for that class. List the three steps for creating an Object for a class? An Object is first declared, then instantiated and then it is initialized.
What is the default value of byte datatype in Java? Default value of byte datatype is 0. What is the default value of float and double datatype in Java? 0f and for double it’s 0.