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Articles by Rishi Raj
Page 3 of 8
Instance variables in Java
Instance variables are declared in a class, but outside a method, constructor or any block.When space is allocated for an object in the heap, a slot for each instance variable value is created.Instance variables are created when an object is created with the use of the keyword 'new' and destroyed when the object is destroyed.Instance variables hold values that must be referenced by more than one method, constructor or block, or essential parts of an object's state that must be present throughout the class.Instance variables can be declared at the class level before or after use.Access modifiers can be given ...
Read MoreHow to extract the first n characters from a string using Java?
To find the consonants in the given String compare every character in it using the charAt() method with the vowel letters and remaining are consonants.Examplepublic class FindingConsonants { public static void main(String args[]) { String str = new String("Hi Welcome to Tutorialspoint"); for(int i=0; i
Read MoreInitializer for final static field in Java
The final static field variable is a constant variable. There is only one copy of this variable available. It is mandatory to initialize the final static field variable explicitly as the default value for it is not provided by the JVM. Also, this variable cannot be reinitialized.A program that initializes the final static field variable using a static initialization block is given as follows:Examplepublic class Demo { final static int num; static { System.out.println("Running static initialization block."); num = 6; } public static void main(String[] args) { ...
Read MoreFinding all words that start with an 'a' in Java
All the words that start with a can be found in a string by using regular expressions in Java. The regular expressions are character sequences that can be used to match other strings using a specific pattern syntax. The regular expressions are available in the java.util.regex package which has many classes but the most important are Pattern class and Matcher class.A program that finds all words that start with an 'a' is using regular expressions is given as follows:Exampleimport java.util.regex.Matcher; import java.util.regex.Pattern; public class Demo { public static void main(String args[]) throws Exception { String str ...
Read MoreA Reluctant qualifier in Java Regular Expressions
The reluctant qualifier starts with the shortest string size as possible. If a match is found by the engine, the process continues to find more matches otherwise the engine adds a character to the searched string section and tries again. This continues until a match is obtained or the string is used up.The regex "B+?" is used to find the match in the string "SkyIsBlue".A program that demonstrates this is given as follows:Exampleimport java.util.regex.Matcher; import java.util.regex.Pattern; public class Demo { public static void main(String args[]) { String regex = "B+?"; String str = ...
Read MoreWhy variables are declared final in Java
A variable cannot be modified after it is declared as final. In other words, a final variable is constant. So, a final variable must be initialized and an error occurs if there is any attempt to change the value.A program that demonstrates a final variable in Java is given as follows −Examplepublic class Demo { public static void main(String[] args) { final double PI = 3.141592653589793; System.out.println("The value of pi is: " + PI); } }OutputThe value of pi is: 3.141592653589793Now let us understand the above program.In the main() method in class ...
Read MoreDuplicating Objects using a Constructor in Java
A copy constructor can be used to duplicate an object in Java. The copy constructor takes a single parameter i.e. the object of the same class that is to be copied. However, the copy constructor can only be explicitly created by the programmer as there is no default copy constructor provided by Java.A program that demonstrates this is given as follows −Exampleclass NumberValue { private int num; public NumberValue(int n) { num = n; } public NumberValue(NumberValue obj) { num = obj.num; } public void display() { ...
Read MorePass long parameter to an overloaded method in Java
Method overloading in a class contains multiple methods with the same name but the parameter list of the methods should not be the same. One of these methods can have a long parameter in their parameter list.A program that demonstrates this is given as follows −Exampleclass PrintValues { public void print(int val) { System.out.println("The int value is: " + val); } public void print(long val) { System.out.println("The long value is: " + val); } } public class Demo { public static void main(String[] args) { PrintValues ...
Read MoreMethods Accepting a Variable Number of objects in Java
A method that accepts a variable number of Object arguments in Java is a form of variable length arguments(Varargs). These can have zero or multiple Object type arguments.A program that demonstrates this is given as follows:Examplepublic class Demo { public static void Varargs(Object... args) { System.out.println("Number of Object arguments are: " + args.length); System.out.println("The Object argument values are: "); for (Object i : args) System.out.println(i); } public static void main(String args[]) { Varargs("Apples", "4", "All"); Varargs("Half of", 3, "is", ...
Read MoreReference static field after declaration in Java
The static field variable is a class level variable and it belongs to the class not the class object.So the static field variable is common to all the class objects i.e. a single copy of the static field variable is shared among all the class objects.A program that demonstrates referencing the static field variable after declaration is given as follows:Examplepublic class Demo { static int a = 7; static int b = a + 5; public static void main(String[] args) { System.out.println("a = " + a); System.out.println("b = " + b); ...
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