Article Categories
- All Categories
-
Data Structure
-
Networking
-
RDBMS
-
Operating System
-
Java
-
MS Excel
-
iOS
-
HTML
-
CSS
-
Android
-
Python
-
C Programming
-
C++
-
C#
-
MongoDB
-
MySQL
-
Javascript
-
PHP
-
Economics & Finance
Object Oriented Programming Articles
Page 258 of 589
What is the difference between String, StringBuffer and StringBuilder classes in Java explain briefly?
The String class of the java.lang package represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class. Strings are constant, their values cannot be changed after they are created.The StringBuffer and StringBuilder classes are used when there is a necessity to make a lot of modifications to Strings of characters.Unlike Strings, objects of type StringBuffer and String builder can be modified over and over again without leaving behind a lot of new unused objects.The StringBuilder class was introduced as of Java 5 and the main difference between the StringBuffer and StringBuilder ...
Read MoreHow can I swap two strings without using a third variable in Java?
To swap the contents of two strings (say s1 and s2) without the third.First of all concatenate the given two strings using the concatenation operator “+” and store in s1 (first string).s1 = s1+s2;The substring method of the String class is used to this method has two variants and returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string or up to endIndex – 1, if the second argument is given.Now using the substring() method of the String class store the ...
Read MoreWhen will be an object eligible for garbage collection?
Java Garbage collector tracks the live object and objects which are no more need are marked for garbage collection. It relieves developers to think of memory allocation/deallocation issues.When an object created in Java program is no longer reachable or used it is eligible for garbage collection.Following are some scenarios where a Java object could be unreachable/unused.Object inside a method − In Java a method is stored in the stack memory. When you call a method, JVM fetches it into the stack and executes it. After the execution it is popped out of the stack then, all its variables will be ...
Read MoreCan I overload private methods in Java?
Overloading is a one of the mechanisms to achieve polymorphism where, a class contains two methods with same name and different parameters.Whenever you call this method the method body will be bound with the method call based on the parameters.Overloading private methodsYes, we can overload private methods in Java but, you can access these from the same class.Examplepublic class Calculator { private int addition(int a , int b){ int result = a+b; return result; } private int addition(int a , int b, int c){ int result = a+b+c; ...
Read MoreCan we cast an object reference to an interface reference in java? If so when?
Yes, you can.If you implement an interface and provide body to its methods from a class. You can hold object of the that class using the reference variable of the interface i.e. cast an object reference to an interface reference.But, using this you can access the methods of the interface only, if you try to access the methods of the class a compile time error is generated.ExampleIn the following Java example, we have an interface named MyInterface with an abstract method display().We have a class with name InterfaceExample with a method (show()). In addition to it, we are implementing the ...
Read MoreCan we create an enum with custom values in java?
Enumeration (enum) in Java is a datatype which stores a set of constant values (Strings in general). You can use enumerations to store fixed values such as days in a week, months in a year etc.enum Days { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY }Custom values to the constantsInstead of declaring just string constants in an enum, you can also have values to these constants as −enum Vehicles { ACTIVA125(80000), ACTIVA5G(70000), ACCESS125(75000), VESPA(90000), TVSJUPITER(75000); }Whenever, you need to assign custom values to the constants of an enum −To hold the value of each ...
Read MoreWhat are the modifiers allowed for methods in an Interface in java?
An interface in Java is a specification of method prototypes. Whenever you need to guide the programmer or, make a contract specifying how the methods and fields of a type should be you can define an interface.In Java 7As of Java7 you can have only public, abstract as modifiers for the methods of an interface.interface MyInterface{ public abstract void display(); public abstract void setName(String name); public abstract void setAge(int age); }Using any other modifier with the methods of an interface would lead to a compile time error.From Java8From Java8 onwards interfaces ...
Read MoreDoes Java support multiple inheritance? Why? How can we resolve this?
Whenever, you extend a class a copy of superclass’s members is available to the subclass object and, when you can call the method of the superclass using the object of the subclass.ExampleIn the following example, we have a class named SuperClass with a method with name demo(). We are extending this class with another class (SubClass).Now, you create an object of the subclass and call the method demo().class SuperClass{ public void demo() { System.out.println("demo method"); } } public class SubClass extends SuperClass { public static ...
Read MoreExplain about field hiding in java?
Whenever you inherit a superclass a copy of superclass’s members is created at the subclass and you using its object you can access the superclass members.If the superclass and the subclass have instance variable of same name, if you access it using the subclass object, the subclass field hides the superclass’s field irrespective of the types. This mechanism is known as field hiding.But, since it makes code complicated field hiding is not recommended.ExampleIn the following example we have two classes Super and Sub one extending the other. They both have two fields with same names (name and age).When we print ...
Read MoreExplain restrictions on using enum in java?
Enumeration (enum) in Java is a datatype which stores a set of constant values. You can use enumerations to store fixed values such as days in a week, months in a year etc.You can define an enumeration using the keyword enum followed by the name of the enumeration as −enum Days { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY }Points to keep in mindYou need to keep the following points in mind while declaring an enum −It is recommended to write the name of the constants in all capital letters as −public class EnumerationExample { enum Days { ...
Read More