In SQL, keys are used to identify records present in a database. The keys used in SQL may look identical but their behaviour is entirely different. The difference between primary, unique and foreign keys is one of the most important concepts in relational database management. The difference between keys is also a common SQL interview […]
Difference Between HAVING Clause and GROUP BY Statements
The difference between the HAVING Clause and GROUP BY statement is common question asked in the database interviews. Both HAVING and GROUP BY are used as an extension of SQL queries. These extended SQL queries are used to filter the rows and return a particular value. HAVING clause and GROUP BY statements play an important […]
Why Inner Class is Used in Java?
The main reason behind the use of inner class is to group the classes with particular logic. This process of grouping classes is called as encapsulation. Increased use of encapsulation in a program will make the code more readable. Why the Use of Inner Class is Necessary in Java? Consider you are using a chat […]
Does Java Pass by Value or Pass by Reference?
Creating copies of values inside the variables and passing the method as arguments is called as “passing by value”. In “pass by value” the actual variable will not be passed. In Java, all arrays, primitive and class types are passed by value. “Pass by reference” is not used in Java. Consider the following code as […]
What is Method Overloading?
If the method present in subclass is similar to the method present in parent class, it is called as method overriding in Java. Method overriding is based on the polymorphism concept of object oriented programming. Method overriding allows the developer to create two methods with same and interface. Method overriding allows the programmer to write […]
What is Java Reflection?
The process of inspecting and changing the runtime behaviour of class during runtime is called as “Java Reflection”. The concept of Java reflection is often confused with the concept of introspection. Introspection can only examine the types and properties of an object during runtime. Java reflection can examine and modify the object during runtime. The […]
What is Inner Class?
Inner classes are the classes which are defined inside a class or interface. Basic Syntax for Inner Class in Java is class OutrClass { class InnrClass { Text goes here… } } If the inner class is compiled using the command javac OutrClass.java. We will get two class files instead of one. OutrClass.class and OutrClass$InnrClass.class […]
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