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Object Oriented Programming Articles
Page 449 of 589
POJO vs Java Beans
As we know that in Java POJO refers to the Plain old Java object.POJO and Bean class in Java shares some common features which are as follows −Both classes must be public i.e accessible to all.Properties or variables defined in both classes must be private i.e. can't be accessed directly.Both classes must have default constructor i.e no argument constructor.Public Getter and Setter must be present in both the classes in order to access the variables/properties.The only difference between both the classes is Java make java beans objects serialized so that the state of a bean class could be preserved in ...
Read MorePrimitive Wrapper Classes are Immutable in Java
In Java Immutable class is a class which once created and it's contents can not be changed.On same concept Immutable objects are the objects whose state can not be changed once constructed.Wrapper classes are made to be immutable due to following advantages −Since the state of the immutable objects can not be changed once they are created they are automatically synchronized.Immutable objects are automatically thread-safe, the overhead caused due to use of synchronisation is avoided.Once created the state of the wrapper class immutable object can not be changed so there is no possibility of them getting into an inconsistent state.The ...
Read MoreHow to test if a Java String contains a case insensitive regex pattern
the syntax? i:x makes the string search case-insensitive. for egpublic class RegCaseSense { public static void main(String[] args) { String stringSearch = "HI we are at java class."; // this won't work because the pattern is in upper-case System.out.println("Try this 1: " + stringSearch.matches(".*CLASS.*")); // the magic (?i:X) syntax makes this search case-insensitive, so it returns true System.out.println("Try this 2: " + stringSearch.matches("(?i:.*CLASS.*)")); } }
Read MoreHow to prevent object of a class from garbage collection in Java?
If a object is no more referenced by a live reference then it becomes eligible for garbage collection. See the example below −Examplepublic class Tester{ public static void main(String[] args) { test(); } public static void test(){ A a = new A(); } } class A {}When test() method complete execution, the a object is no more referenced and is eligible for garbage collection. Java garbage collector will deallocate the object when it runs.To prevent garbage collection, we can create a static reference to an object and then ...
Read MoreGenerating password in Java
Generate temporary password is now a requirement on almost every website now-a-days. In case a user forgets the password, system generates a random password adhering to password policy of the company. Following example generates a random password adhering to following conditions −It should contain at least one capital case letter.It should contain at least one lower-case letter.It should contain at least one number.Length should be 8 characters.It should contain one of the following special characters: @, $, #, !.Exampleimport java.util.Random; public class Tester{ public static void main(String[] args) { System.out.println(generatePassword(8)); } private ...
Read MoreGenerating random numbers in Java
We can generate random numbers using three ways in Java.Using java.util.Random class − Object of Random class can be used to generate random numbers using nextInt(), nextDouble() etc. methods.Using java.lang.Math class − Math.random() methods returns a random double whenever invoked.Using java.util.concurrent.ThreadLocalRandom class − ThreadLocalRandom.current().nextInt() method and similar othjer methods return a random numbers whenever invoked.Exampleimport java.util.Random; import java.util.concurrent.ThreadLocalRandom; public class Tester { public static void main(String[] args) { generateUsingRandom(); generateUsingMathRandom(); generateUsingThreadLocalRandom(); } private static void generateUsingRandom() { Random random = new Random(); ...
Read MoreGenerating OTP in Java
Generate OTP is now a requirement on most of the website now-a-days. In case of additional authentication, system generates a OTP password adhering to OTP policy of the company. Following example generates a unique OTP adhering to following conditions −It should contain at least one number.Length should be 4 characters.Exampleimport java.util.Random; public class Tester { public static void main(String[] args) { System.out.println(generateOTP(4)); } private static char[] generateOTP(int length) { String numbers = "1234567890"; Random random = new Random(); char[] otp = new ...
Read MoreFlow control in a try catch finally in Java
A method catches an exception using a combination of the try and catch keywords. A try/catch block is placed around the code that might generate an exception. Code within a try/catch block is referred to as protected code, and the syntax for using try/catch looks like the following −Syntaxtry { // Protected code } catch (ExceptionName e1) { // Catch block }The code which is prone to exceptions is placed in the try block. When an exception occurs, that exception occurred is handled by catch block associated with it. Every try block should be immediately followed either by ...
Read Morefinal local variable in Java
Local VariableLocal variables are declared in methods, constructors, or blocks.Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or block.Access modifiers cannot be used for local variables.Local variables are visible only within the declared method, constructor, or block.Local variables are implemented at stack level internally.There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.final Local Variablefinal is the only allowed access modifier for local variables.final local variable is not required ...
Read MoreFinal static variables in Java
Final Static VariablesClass variables also known as static variables are declared with the static keyword in a class, but outside a method, constructor or a block.There would only be one copy of each class variable per class, regardless of how many objects are created from it.Static variables are normally declared as constants using the final keyword. Constants are variables that are declared as public/private, final, and static. Constant variables never change from their initial value.Static variables are stored in the static memory, mostly declared as final and used as either public or private constants.Static variables are created when the program ...
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