Top 30 Java Programming Interview Questions
Check out Top 30 Java Programming Interview Questions and answers that are very useful for freshers/experienced aspirants. Given below are some important Java Programming questions that are often asked in interview session from the aspirants. Moreover, interested aspirants can download the PDF for interview programming questions on collections in java from here.
Top 30 Java Programming Interview Questions and Answers
About Interview Programming Questions In Java:
Top java programming interview questions are some programming exercises which are asked to be solved in java programming language in limited time during any core Java or J2EE interview. These java collections programming interview questions are collected from different sources.
What is Java Programming?
Java is computer programming language that is designed to have as few implementation dependencies as possible. Java Virtual Machine (JVM) is used to run Java as it executes the Java byte code. For the security of Java applications, Java platform provides automatic memory management and it also reduces memory corruption and vulnerabilities.
Core Java Interview Programming Questions and Answers:
“Core Java” is Sun’s term, used to refer to Java SE, the standard edition and a set of connected technologies, like the Java VM, CORBA, etc. Check below listed basic java programming interview questions and prepare well for interview session.
Question 1: What is a transient variable?
Answer: A transient variable is a variable that may not be serialized.
Question 2: Which containers use a border Layout as their default layout?
Answer: The Window, Frame, and Dialog classes use a border layout as their default layout.
Question 3: Why do threads block on I/O?
Answer: Threads block on I/O (that is enters the waiting state) so that other threads may execute while the I/O Operation is performed.
Question 4: Can a lock be acquired on a class?
Answer: Yes, a lock can be acquired on a class. This lock is acquired on the class’s Class object.
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Question 5: Is null a keyword?
Answer: The null is not a keyword.
Question 6: What is the preferred size of a component?
Answer: The preferred size of a component is the minimum component size that will allow the component to display normally.
Question 7: What method is used to specify a container’s layout?
Answer: The setLayout () method is used to specify a container’s layout.
Question 8: Which containers use a FlowLayout as their default layout?
Answer: The Panel and Applet classes use the FlowLayout as their default layout.
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Question 9: What is the Collections API?
Answer: The Collections API is a set of classes and interfaces that support operations on collections of objects.
Question 10: Which characters may be used as the second character of an identifier, but not as the first character of an identifier?
Answer: The digits 0 through 9 may not be used as the first character of an identifier but they may be used after the first character of an identifier.
Question 11: What is the List interface?
Answer: The List interface provides support for ordered collections of objects.
Question 12: How does Java handle integer overflows and underflows?
Answer: It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.
Question 13: What is the Vector class?
Answer: The Vector class provides the capability to implement a growable array of objects
Question 14: What modifiers may be used with an inner class that is a member of an outer class?
Answer: A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.
Question 15: What is an Iterator interface?
Answer: The Iterator interface is used to step through the elements of a Collection.
Question 16: Which method of the Component class is used to set the position and size of a component?
Answer: setBounds() method is used to set the position and size of a component.
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Question 17: Which java.util classes and interfaces support event handling?
Answer: The EventObject class and the EventListener interface support event processing.
Question 18: Is sizeof a keyword?
Answer: The sizeof operator is not a keyword.
Question 19: What are wrapped classes?
Answer: Wrapped classes are classes that allow primitive types to be accessed as objects.
Question 20: What is the immediate superclass of the Applet class?
Question 21: Name three Component subclasses that support painting.
Answer: The Canvas, Frame, Panel, and Applet classes support painting.
Question 22: What value does readLine() return when it has reached the end of a file?
Answer: The readLine() method returns null when it has reached the end of a file.
Question 23: What is clipping?
Answer: Clipping is the process of confining paint operations to a limited area or shape.
Question 24: What is a native method?
Answer: A native method is a method that is implemented in a language other than Java.
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Question 25: What if I write static public void instead of public static void?
Answer: Program compiles and runs properly.
Question 26: What if I do not provide the String array as the argument to the method?
Answer: Program compiles but throws a runtime error “NoSuchMethodError”.
Question 27: If I do not provide any arguments on the command line, then the String array of main() method will be empty or null?
Answer: It is empty. But not null.
Question 28: What is the difference between String, StringBuilder, and StringBuffer in Java?
Answer: The main difference is that String is immutable but both StringBuilder and StringBuffer are mutable. Also, StringBuilder is not synchronized like StringBuffer and that’s why faster and should be used for temporary String manipulation.
Question 29: Why String is final in Java?
Answer: The string is final because of same reason it is immutable. Couple of reasons which I think make sense is an implementation of String pool, Security, and Performance. Java designers know that String will be used heavily in every single Java program, so they optimized it from the start.
Question 30: How to Split String in Java?
Answer: Java API provides several convenient methods to split a string based upon any delimiter e.g. comma, semicolon or colon. You can even use a regular expression to split a big string into several smaller strings.
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