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Java Articles
Page 114 of 450
What is the difference between simple name, canonical name and class name in a Java class?
Canonical name of a Java class is the name of the class along with the package. For example, the canonical name of the class File is java.io.File. You can also get the canonical name of a particular class using Java method. The class named Class provides a method getCanonicalName(), this method returns canonical name of the current class. Example import java.lang.*; public class ClassDemo { public static void main(String[] args) { ClassDemo c = new ClassDemo(); Class cls = c.getClass(); ...
Read MoreHow to declare, define and call a method in Java?
Following is the syntax to declare a method in Java. Syntax modifier return_type method_name(parameters_list){ //method body } Where, modifier − It defines the access type of the method and it is optional to use. return_type − Method may return a value. method_name − This is the method name. The method signature consists of the method name and the parameter list. parameters_list − The list of parameters, it is the type, order, and a number of parameters of a method. These are optional, method may contain zero parameters. method body − The method body defines ...
Read MoreWhat are static members of a Java class?
In Java, static members are those which belongs to the class and you can access these members without instantiating the class. The static keyword can be used with methods, fields, classes (inner/nested), blocks. Static Methods − You can create a static method by using the keyword static. Static methods can access only static fields, methods. To access static methods there is no need to instantiate the class, you can do it just using the class name as − Example public class MyClass { public static void sample(){ System.out.println("Hello"); ...
Read MoreHow can I put a Java arrays inside an array?
Exampleimport java.util.Arrays; public class ArrayWithinAnArray{ public static void main(String args[]) { int[] myArray1 = {23, 56, 78, 91}; int[] myArray2 = {123, 156, 178, 191}; int[] myArray3 = {223, 256, 278, 291}; int[] myArray4 = {323, 356, 378, 391}; int [][] arrayOfArrays = {myArray1, myArray2, myArray3, myArray4}; System.out.println(Arrays.deepToString(arrayOfArrays)); } }Output[[23, 56, 78, 91], [123, 156, 178, 191], [223, 256, 278, 291], [323, 356, 378, 391]]
Read MoreWhat is the lambda expression to convert array/List of String to array/List of Integers in java?
You can convert an array list of strings to an array list of integers as:Exampleimport java.util.ArrayList; import java.util.List; import java.util.stream.Collectors; public class LamdaExpressions { public static void main(String args[]) { ArrayList list = new ArrayList(); list.add("123"); list.add("223"); list.add("323"); list.add("334"); List listInteger = list.stream().map(s -> Integer.parseInt(s)).collect(Collectors.toList()); System.out.println(listInteger); } }Output[123, 223, 323, 334]
Read MoreWhat is a method signature in Java?
The method signature consists of the method name and the parameter list. Example public class MethodSignature { public int add(int a, int b){ int c = a+b; return c; } public static void main(String args[]){ MethodSignature obj = new MethodSignature(); int result = obj.add(56, 34); System.out.println(result); } } Output 90 Method signature does not ...
Read MoreShould a constructor always have the same name as the class in java?
Yes, the constructor should always have the same name as the class. Constructor looks like method but it is not. It does not have a return type and its name is same as the class name. Mostly it is used to instantiate the instance variables of a class. If the programmer doesn’t write a constructor the compiler writes a constructors on his behalf. Example public class Sample{ public Sample(){ System.out.println("This is a constructor"); } public static void main(String args[]){ Sample obj = new Sample(); } } Output This is a constructor
Read MoreWhat is the class "class" in Java?
The Java.lang.Class class instance represent classes and interfaces in a running Java application. It has no public constructor. Example Following is the example demonstrates the usage of the class Class. The java.lang.Class.getCanonicalName() method returns the canonical name of the underlying class as defined by the Java Language Specification. It returns null if the class does not have a canonical name. import java.lang.*; public class ClassDemo { public static void main(String[] args) { ClassDemo c = new ClassDemo(); Class cls = c.getClass(); ...
Read MoreWhat is the difference between super and this, keywords in Java?
The this is a keyword in Java which is used as a reference to the object of the current class. Using it you can − Differentiate the instance variables from local variables if they have same names, within a constructor or a method. Call one type of constructor (parametrized constructor or default) from other in a class. It is known as explicit constructor invocation. Example class Superclass { int age; Superclass(int age) { this.age = age; } public void ...
Read MoreHow to execute a static block without main method in Java?
VM first looks for the main method (at least the latest versions) and then, starts executing the program including static block. Therefore, you cannot execute a static block without main method. Example public class Sample { static { System.out.println("Hello how are you"); } } Since the above program doesn’t have a main method, If you compile and execute it you will get an error message. C:\Sample>javac StaticBlockExample.java C:\Sample>java StaticBlockExample Error: Main method not found in class StaticBlockExample, please define the main method as: public static ...
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