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Q92. What is the difference between System.console.write and System.out.println ?
Ans. System.console() returns null if your application is not run in a terminal (though you can handle this in your application)System.console() provides methods for reading password without echoing charactersSystem.out and System.err use the default platform encoding, while the Console class output methods use the console encoding
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Ans. You can put related classes together as a single logical group.
Nested classes can access all class members of the enclosing class, which might be useful in certain cases.
Nested classes are sometimes useful for specific purposes. For example, anonymous inner classes are useful for writing simpler event-handling code with AWT/Swing.
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Ans. The accessibility (public, protected, etc.) of the static nested class is defined by the outer class.
A static nested class is not an inner class, it's a top-level nested class.
The name of the static nested class is expressed with OuterClassName.NestedClassName syntax.
When you define an inner nested class (or interface) inside an interface, the nested class is declared implicitly public and static.
Static nested classes can be declared abstract or final.
Static nested classes can extend another class or it can be used as a base class.
Static nested classes can have static members.
Static nested classes can access the members of the outer class (only static members, obviously).
The outer class can also access the members (even private members) of the nested class through an object of nested class. If you don't declare an instance of the nested class, the outer class cannot access nested class elements directly.
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Ans. The accessibility (public, protected, etc.) of the inner class is defined by the outer class.
Just like top-level classes, an inner class can extend a class or can implement interfaces.
Similarly, an inner class can be extended by other classes, and an inner interface can be implemented or extended by other classes or interfaces.
An inner class can be declared final or abstract.Inner classes can have inner classes, but you will have a hard time reading or understanding such complex nesting of classes.
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Ans. You can create a non-static local class inside a body of code. Interfaces cannot have local classes, and you cannot create local interfaces.
Local classes are accessible only from the body of the code in which the class is defined. The local classes are completely inaccessible outside the body of the code in which the class is defined.
You can extend a class or implement interfaces while defining a local class.
A local class can access all the variables available in the body of the code in which it is defined. You can pass only final variables to a local inner class.
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Ans. Anonymous classes are defined in the new expression itself, so you cannot create multiple objects of an anonymous class.
You cannot explicitly extend a class or explicitly implement interfaces when defining an anonymous class.
An anonymous inner class is always created as part of a statement; don't forget to close the statement after the class definition with a curly brace. This is a rare case in Java, a curly brace followed by a semicolon.
Anonymous inner classes have no name, and their type must be either a subclass of the named type or an implementer of the named interface
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Ans. A class is a blue print or Mold using which individual objects are created. A class can contain fields and methods to describe the behavior of an object.
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Ans. We can use String getBytes() method to convert String to byte array and we can use String constructor new String(byte[] arr) to convert byte array to String.
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Ans. PATH is the variable that holds the directories for the OS to look for executables. CLASSPATH is the variable that holds the directories for JVM to look for .class files ( Byte Code ).
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Ans. Compile Time Error: Unhandled exception type Exception
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Q108. Does SQL allow null values ? Can we use it within Where clause ?
Ans. Yes , we can have null values for columns in SQL. Null value represent that the columns value is unknown or haven't been filled. Yes, We can use it within where clause to get the rows with null values.
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Ans. No. It gives the error "Cannot Instantiate the type Calendar". Calendar is an abstract class and hence Calendar object should be instantiated using Calendar.getInstance().
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Ans. Assert works only if assertions ( -ea ) are enabled which is not required for Verify.Assert throws an exception and hence doesn't continue with the test if assert evaluates to false whereas it's not so with Verify.
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Ans. Yes but as Hibernate creates the Proxy Classes inherited from the Entity Classes to communicate with Database for lazy initialization. Declaring entity classes as final will prohibit communication with database lazily and hence will be a performance hit.
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Q117. How do you define a class of constants in Java?
Ans. Make the class as final. Disable the object construction by making constructor private. Keep only Static Final Variables declared and Defined at the same time.
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Q119. Shouldn't we make a class with all static members is its just expected to be executed as a standalone program with just one thread. Moreover Lets assume that there is no runtime Polymorphism required and there is no need for serialization ?
Ans. Still No in case we are making use of inheritance. we may have problem wherein we have program flow moving across common inherited method and specific methods of the derived class. call made to another static method in the parent class will only access the static class of the Parent class irrespective of the call from any of the derived class.
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Which of following can be nested into another ?
