What are differences between Swing and AWT?
One of the classic java swing interview questions and mostly asked on phone interviews. There is couple of differences between swing and AWT:
1) AWT component are considered to be heavyweight while Swing componentare lightweights
2) Swing has plug-gable look and feel.
3) AWT is platform depended same GUI will look different on different platform while Swing is developed in Java and is platform dependent.
WhySwing components are called lightweight component?
Another popular java swing interview question, I guess the oldest that is generally comes as followup of earlier question based on your answer provided.AWT components are associated with native screen resource and called heavyweight component while Swing components is uses the screen resource of an ancestor instead of having there own and that's why called lightweight or lighter component.
Writecode to print following layout (mainly focused on GridBag layout)?
After JTable second favorite topic of swing interviewer is GridBagLayout. GridBagLayout in swing is most powerful but at same time most complex layout and a clear cut experience and expertise around GridBagLayout is desired for developing Swing GUI for trading systems. No matter whether you are developing GUI for equities trading, futures or options trading or forex trading you always required GridBagLayout. Swing interview question on GridBagLayout willbe mostly on writing code for a particular layout just like an example shown here. In which six buttons A, B, C, D, E and F are organized in certain fashion.
How do you handle opening of database, file or network connection on a click of button?
This one is one of the easy java swing interview question. Interviewer is interested on whether you know the basic principle of Java GUI development or not. answer is you should not do this operation in EDT thread instead spawn a new thread from action Listener or button and disable the button until operation gets completed to avoid resubmitting request. Only condition is that your GUI should always be responsive no matter what happens on network connection or database connection because these operations usually take time.
Predictionof output of code?
This is another category of Swing interview questions asked in IB whether they will give you code and asked what would be the output , how will the GUI look like. This type of question is based upon how well you understand and visualize the code. Whether you are familiar with default layout manager of various component classes or not e.g. default layout of JFrame is BorderLayout.So do some practice of these kinds of java Swing interview questions as well?
What is the difference between Assignment and Initialization?- Assignment can be done as many times as desired whereas initialization can be done only once.
What is OOPs?- Object oriented programming organizes a program around its data, i. e. , objects and a set of well defined interfaces to that data. An object-oriented program can be characterized as data controlling access to code.
What are Class, Constructor and Primitive data types?- Class is a template for multiple objects with similar features and it is a blue print for objects. It defines a type of object according to the data the object can hold and the operations the object canper form. Constructor is a special kind of method that determines how an object is initialized when created. Primitive data types are 8 types and they are:byte, short, int, long, float, double, boolean, char.
What is an Object and how do you allocate memory to it?- Object is an instance of a class and it is a software unit that combines a structured set of data with a set of operations for inspecting and manipulating that data. When an object is created using new operator,memory is allocated to it.
What is the difference between constructor and method?- Constructor will be automatically invoked when an object is created whereas method has to be called explicitly.
What are methods and how are they defined?-Methods are functions that operate on instances of classes in which they are defined. Objects can communicate with each other using methods and can call methods in other classes. Method definition has four parts. They are name of the method, type of object or primitive type the method returns, a list of parameters and the body of the method. A method’s signature is a combination of the first three parts mentioned above.
What is the use of bin and lib in JDK?-Bin contains all tools such as java c, applet viewer, awt tool, etc., whereas lib contains API and all packages.
What is casting?- Casting is used to convert the value of one type to another.
How many ways can an argument be passed to a subroutine and explain them?- An argument can be passed in two ways. They are passing byvalue and passing by reference. Passing by value: This method copies the value of an argument into the formal parameter of the subroutine. Passing by reference: In this method, a reference to an argument (not the value of the argument) is passed to the parameter.
What is Event-Driven-Thread (EDT) in Swing?
Event-Driven-Thread or EDT is a special thread in Swing and AWT.Event-Driven Thread is used to draw graphics and listen for events in Swing.You will get a bonus point if you able to highlight that time consuming operations like connecting to database, opening a file or connecting to network should not be done on EDT thread because it could lead to freezing GUI because of blocking and time consuming nature of these operations instead they should be done on separate thread and EDT can just be used to spawn those thread on a button click or mouse click.
Does Swing is thread safe? What do you mean by swing is not thread-safe?
This swing interview questions is getting very popular now days. Though it’s pretty basic many developer doesn't understand thread-safety issue in Swing. Since Swing components are not thread-safe it means you can not update these components in any thread other than Event-Driven-Thread. If you do so you will get unexpected behavior. Some time interviewer will also ask what are thread-safe methods in swing which can be safely called from any thread only few like repaint() and revalidate().
What is the difference between an argument and a parameter?- While defining method, variables passed in the method are called parameters. While using those methods, values passed to those variables are called arguments.
What are different types of access modifiers?-public: Any thing declared as public can be accessed from anywhere. private:Any thing declared as private can’t be seen outside of its class. protected:Any thing declared as protected can be accessed by classes in the same package and subclasses in the other packages. default modifier : Can be accessed only to classes in the same package.
What is final, finalize() and finally?-final : final keyword can be used for class, method and variables. A final class cannot be sub classed and it prevents other programmers from sub classing a secure class to invoke insecure methods. A final method can’t be overridden. A final variable can’t change from its initialized value. finalize() : finalize()method is used just before an object is destroyed and can be called just prior to garbage collection. finally : finally, a key word used in exception handling, creates a block of code that will be executed after a try/catch block has completed and before the code following the try/catch block. The finally block will execute whether or not an exception is thrown. For example, if a method opens a file upon exit, then you will not want the code that closes the file to be bypassed by the exception-handling mechanism. This finally keyword is designed to address this contingency.
What is UNICODE?- Unicode is used for internal representation of characters and strings and it uses 16 bits to represent each other.
What is Garbage Collection and how to call it explicitly?- When an object is no longer referred to by any variable,java automatically reclaims memory used by that object. This is known as garbage collection. System. gc() method may be used to call it explicitly.
What is finalize() method?- finalize () method is used just before an object is destroyed and can be called just prior to garbage collection.
What are Transient and Volatile Modifiers?-Transient: The transient modifier applies to variables only and it is not stored as part of its object’s Persistent state. Transient variables are not serialized. Volatile: Volatile modifier applies to variables only and it tells the compiler that the variable modified by volatile can be changed unexpectedly by other parts of the program.
What is method overloading and method overriding?-Method overloading: When a method in a class having the same method name with different arguments is said to be method overloading. Method overriding : When a method in a class having the same method name with same arguments is said to be method overriding.
What is difference between overloading and overriding?- a) In overloading, there is a relationship between methods available in the same class whereas in overriding, there is relationship between a super class method and subclass method. b) Overloading does not block inheritance from the super class whereas overriding blocks inheritance from the super class. c) In overloading, separate methods share the same name whereas in overriding, subclass method replaces the super class. d) Overloading must have different method signatures whereas overriding must have same signature.
What is meant by Inheritance and what are its advantages?- Inheritance is the process of inheriting all the features from a class. The advantages of inheritance are reusability of code and accessibility of variables and methods of the super class by subclasses.
What is the difference between this() and super()?-this() can be used to invoke a constructor of the same class whereas super()can be used to invoke a super class constructor.
What is the difference between super class and subclass?- A super class is a class that is inherited whereas subclass is a class that does the inheriting.
What modifiers may be used with top-level class?-public, abstract and final can be used for top-level class.
What are inner class and anonymous class?-Inner class : classes defined in other classes, including those defined in methods are called inner classes. An inner class can have any accessibility including private. Anonymous class : Anonymous class is a class defined inside a method without a name and is instantiated and declared in the same place and cannot have explicit constructors.
What is a package?- A package is a collection of classes and interfaces that provides a high-level layer of access protection and name space management.
What is a reflection package?- java.lang. reflect package has the ability to analyze itself in run time.
What is interface and its use?- Interface is similar to a class which may contain method’s signature only but not bodies and it is a formal set of method and constant declarations that must be defined by the class that implements it. Interfaces are useful for: a)Declaring methods that one or more classes are expected to implement b)Capturing similarities between unrelated classes without forcing a class relationship. c)Determining an object’s programming interface without revealing the actual body of the class.
What is an abstract class?- An abstract class is a class designed with implementation gaps for subclasses to fill in and is deliberately incomplete.
What is the difference between Integer and int?-a) Integer is a class defined in the java. lang package, whereas int is a primitive data type defined in the Java language itself. Java does not automatically convert from one to the other. b) Integer can be used as an argument for a method that requires an object, whereas int can be used for calculations.
What is a cloneable interface and how many methods does it contain?- It is not having any method because it is a TAGGED or MARKER interface.
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