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Java Articles
Page 302 of 450
Accessing variables of two interfaces, which are same from an implementing class in java?
An interface in Java is similar to class but, it contains only abstract methods and fields which are final and static.You can implement multiple interfaces using a single class in Java. Whenever both interfaces have same name, since all the fields of an interface are static by default, you can access them using the name of the interface as −Exampleinterface MyInterface1{ public static int num = 100; public void display(); } interface MyInterface2{ public static int num = 1000; public void show(); } public class InterfaceExample implements MyInterface1, MyInterface2{ public static int num = 10000; ...
Read MoreWhat happens if we does not initialize variables of an interface in java?
In Java final is the access modifier which can be used with a filed class and a method.When a method if final it cannot be overridden.When a variable is final its value cannot be modified further.When a class is finale it cannot be extended.Declaring final variable without initializationIf you declare a variable as final, it is mandatory to initialize it before the end of the constructor. If you don’t you will get a compilation error.ExampleIn the following java program, we a have an interface with a public, static, final variable with name num and, a public, abstract method with name ...
Read MoreCan we create non static variables in an interface using java?
Interface in Java is similar to class but, it contains only abstract methods and fields which are final and static.Since all the methods are abstract you cannot instantiate it. To use it, you need to implement this interface using a class and provide body to all the abstract methods int it.Non static variables in an interfaceNo you cannot have non-static variables in an interface. By default, All the members (methods and fields) of an interface are publicAll the methods in an interface are public and abstract (except static and default).All the fields of an interface are public, static and, final ...
Read MoreWhat happens if we define a concrete method in an interface in java?
Interface in Java is similar to class but, it contains only abstract methods and fields which are final and static.Since all the methods are abstract you cannot instantiate it. To use it, you need to implement this interface using a class and provide body to all the abstract methods int it.Concrete methods in an interfaceAll the methods in an interface must be abstract, you cannot have a concrete method (the one which has body) if you try to do so, it gives you a compile time error saying “interface abstract methods cannot have body”.ExampleIn the following Java program, we are ...
Read MoreCan we create an object for the abstract class in java?
A method which does not have body is known as abstract method. It contains only method signature with a semi colon and, an abstract keyword before it.public abstract myMethod();To use an abstract method, you need to inherit it by extending its class and provide implementation to it.A class which contains 0 or more abstract methods is known as abstract class. If it contains at least one abstract method, it must be declared abstract.Instantiating an abstract classOnce a class is abstract it indicates that it may contain incomplete methods hence you cannot create an object of the abstract class.If you try ...
Read MoreIs there any alternative solution for static constructor in java?
The main purpose of constructors in Java is to initialize the instance variables of a class.But, if a class have Static variables you cannot initialize them using the constructors (you can assign values to static variables in constructors but in that scenario, we are just assigning values to static variables). because static variables are loaded into the memory before instantiation (i.e. before constructors are invoked)So, we should initialize static variables from static context. We cannot use static before constructors, Therefore, as an alternation to you can use static blocks to initialize static variables.Static blockA static block is a block of ...
Read MoreCan we return this keyword from a method in java?
The "this" keyword in Java is used as a reference to the current object, within an instance method or a constructor. Using this you can refer the members of a class such as constructors, variables, and methods.Returning “this”Yes, you can return this in Java i.e. The following statement is valid.return this;When you return "this" from a method the current object will be returned.ExampleIn the following Java example, the class Student has two private variables name and age. From a method setValues() we are reading values from user and assigning them to these (instance) variables and returning the current object.public class Student ...
Read MoreGet Array Dimensions in Java
In order to get Array Dimensions in Java, we use the getClass(), isArray() and getComponentType() methods with decision making in combination with iterative statements.The getClass() method method returns the runtime class of an object. The getClass() method is a part of the java.lang.Object class.Declaration − The java.lang.Object.getClass() method is declared as follows −public final Class getClass()The isArray() method checks whether the passed argument is an array. It returns a boolean value, either true or falseSyntax - The isArray() method has the following syntaxArray.isArray(obj)The getComponentType() method returns the Class denoting the component type of an array. If the class is not an ...
Read MoreHow can we retrieve file from database using JDBC?
The ResultSet interface provides the methods named getClob() and getCharacterStream() to retrieve Clob datatype, In which the contents of a file are typically stored.These methods accept an integer representing the index of the column (or, a String value representing the name of the column) and retrieves the value at the specified column.The difference is the getClob() method returns a Clob object and the getCgaracterStream() method returns a Reader object which holds the contents of the Clob datatype.ExampleAssume we have created a table named Articles in the database with the following description.+---------+--------------+------+-----+---------+-------+ | Field | Type ...
Read MoreExplain the ODBC architecture?
ODBC architecture consists of the following components.Application: An application which communicates with the databases using ODBC functions is an ODBC application.ODBC driver manager: The ODBC diver manager manages the underlying drivers in an application. Whenever an application calls a function of ODBC API to communicate with a database, the driver manager accepts those function calls and passes them to the ODBC driver. When the driver retrieves the results from the database the driver manager accepts the results from the driver and returns it back to the application.ODBC driver: The ODBC driver accepts the application function calls from the driver manager ...
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