General Interview Questions on Java

• What do you know about Java?
• What are the supported platforms by Java Programming Language?
• List any five features of Java?
• Why is Java Architectural Neutral?
• How Java enabled High Performance?
• Why Java is considered dynamic?
• What is Java Virtual Machine and how it is considered in context of Java’s platform independent feature?
• List two Java IDE’s?
• List some Java keywords(unlike C, C++ keywords)?
• What do you mean by Object?
• Define class?
• What kind of variables a class can consist of?
• What is a Local Variable?
• What is a Instance Variable?
• What is a Class Variable?
• What is Singleton class?
• What do you mean by Constructor?
• List the three steps for creating an Object for a class?
• What is the default value of byte datatype in Java?
• What is the default value of float and double datatype in Java?
• When a byte datatype is used?
• What is a static variable?
• What do you mean by Access Modifier?
• What is protected access modifier?
• What do you mean by synchronized Non Access Modifier?
• According to Java Operator precedence, which operator is considered to be with highest precedence?
• Variables used in a switch statement can be used with which datatypes?
• When parseInt() method can be used?
• Why is String class considered immutable?
• Why is StringBuffer called mutable?
• What is the difference between StringBuffer and StringBuilder class?
• Which package is used for pattern matching with regular expressions?
• java.util.regex consists of which classes?
• What is finalize() method?
• What is an Exception?
• What do you mean by Checked Exceptions?
• Explain Runtime Exceptions?
• Which are the two subclasses under Exception class?
• When throws keyword is used?
• When throw keyword is used?
• How finally used under Exception Handling?
• What things should be kept in mind while creating your own exceptions in Java?
• Define Inheritance?
• When super keyword is used?
• What is Polymorphism?
• What is Abstraction?
• What is Abstract class?
• When Abstract methods are used?
• What is Encapsulation?
• What is the primary benefit of Encapsulation?
• What is an Interface?
• Give some features of Interface?
• Define Packages in Java?
• Why Packages are used?
• What do you mean by Multithreaded program?
• What are the two ways in which Thread can be created?
• What is an applet?
• An applet extend which class?
• Explain garbage collection in Java?
• Define immutable object?
• Explain the usage of this() with constructors?
• Explain Set Interface?
• Explain TreeSet?
• What is Comparable Interface?
• Difference between throw and throws?
• Explain the following line used under Java Program −
• public static void main (String args[ ])
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• Define JRE i.e. Java Runtime Environment?
• What is JAR file?
• What is a WAR file?
• Define JIT compiler?
• What is the difference between object oriented programming language and object based programming language?
• What is the purpose of default constructor?
• Can a constructor be made final?
• What is static block?
• Define composition?
• What is function overloading?
• What is function overriding?
• Difference between Overloading and Overriding?
• What is final class?
• What is NullPointerException?
• What are the ways in which a thread can enter the waiting state?
• How does multi-threading take place on a computer with a single CPU?
• What invokes a thread's run() method?
• Does it matter in what order catch statements for FileNotFoundException and IOException are written?
• What is the difference between yielding and sleeping?
• Why Vector class is used?
• How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?
• What are Wrapper classes?
• What is the difference between a Window and a Frame?
• Which package has light weight components?
• What is the difference between the paint() and repaint() methods?
• What is the purpose of File class?
• What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?
• Which class should you use to obtain design information about an object?
• What is the difference between static and non-static variables?
• What is Serialization and deserialization?
• What are use cases?
• Explain the use of sublass in a Java program?
• How to add menushortcut to menu item?
• Can you write a Java class that could be used both as an applet as well as an application?
• What is the difference between Swing and AWT components?
• What's the difference between constructors and other methods?
• Is there any limitation of using Inheritance?
• When is the ArrayStoreException thrown?
• Can you call one constructor from another if a class has multiple constructors?
• What's the difference between the methods sleep() and wait()?
• When ArithmeticException is thrown?
• What is a transient variable?
• What is synchronization?
• What is the Collections API?
• Does garbage collection guarantee that a program will not run out of memory?
• The immediate superclass of the Applet class?
• Which Java operator is right associative?
• What is the difference between a break statement and a continue statement?
• If a variable is declared as private, where may the variable be accessed?
• What is the purpose of the System class?
• List primitive Java types?
• What is the relationship between clipping and repainting under AWT?
• Which class is the immediate superclass of the Container class?
• What class of exceptions are generated by the Java run-time system?
• Under what conditions is an object's finalize() method invoked by the garbage collector?
• How can a dead thread be restarted?
• Which arithmetic operations can result in the throwing of an ArithmeticException?
• Variable of the boolean type is automatically initialized as?
• Can try statements be nested?
• What are ClassLoaders?
• What is the difference between an Interface and an Abstract class?
• What will happen if static modifier is removed from the signature of the main method?
• What is the default value of an object reference declared as an instance variable?
• Can a top level class be private or protected?
• Why do we need wrapper classes?
• What is the difference between error and an exception?
• Is it necessary that each try block must be followed by a catch block?
• When a thread is created and started, what is its initial state?
• What is the Locale class?
• What are synchronized methods and synchronized statements?
• What is runtime polymorphism or dynamic method dispatch?
• What is Dynamic Binding(late binding)?
• Can constructor be inherited?
• What are the advantages of ArrayList over arrays?
• Why deletion in LinkedList is fast than ArrayList?
• How do you decide when to use ArrayList and LinkedList?
• What is a Values Collection View ?
• What is dot operator?
• Where and how can you use a private constructor?
• What is type casting?
• Describe life cycle of thread?
• What is the difference between the >> and >>> operators?
• Which method of the Component class is used to set the position and size of a component?
• What is the range of the short type?
• What is the immediate superclass of Menu?
• Does Java allow Default Arguments?
• Which number is denoted by leading zero in java?
• Which number is denoted by leading 0x or 0X in java?
• Break statement can be used as labels in Java?
• Where import statement is used in a Java program?
• Explain suspend() method under Thread class>
• Explain isAlive() method under Thread class?
• What is currentThread()?
• Explain main thread under Thread class execution?
• Life cycle of an applet includes which steps?
• Why is the role of init() method under applets?
• Which method is called by Applet class to load an image?
• Define code as an attribute of Applet?
• Define canvas?
• Define Network Programming?
• What is a Socket?
• Advantages of Java Sockets?
• Disadvantages of Java Sockets?
• Which class is used by server applications to obtain a port and listen for client requests?
• Which class represents the socket that both the client and server use to communicate with each other?
• Why Generics are used in Java?
• What environment variables do I need to set on my machine in order to be able to run Java programs?
• Is there any need to import java.lang package?
• What is Nested top-level class?
• What is Externalizable interface?
• If System.exit (0); is written at the end of the try block, will the finally block still execute?
• What is daemon thread?
• Which method is used to create the daemon thread?
• Which method must be implemented by all threads?
• What is the GregorianCalendar class?
• What is the SimpleTimeZone class?
• What is the difference between the size and capacity of a Vector?
• Can a vector contain heterogenous objects?
• What is an enumeration?
• What is difference between Path and Classpath?
• Can a class declared as private be accessed outside it's package?
• What are the restriction imposed on a static method or a static block of code?
• Can an Interface extend another Interface?
• Which object oriented Concept is achieved by using overloading and overriding?
• What is an object's lock and which object's have locks?
• What is Downcasting?
• What are order of precedence and associativity and how are they used?
• If a method is declared as protected, where may the method be accessed?
• What is the difference between inner class and nested class?
• What restrictions are placed on method overriding?
• What is constructor chaining and how is it achieved in Java?
• Can a double value be cast to a byte?
• How does a try statement determine which catch clause should be used to handle an exception?
• What will be the default values of all the elements of an array defined as an instance variable?