With Java 9, new factory methods are added to Map interface to create immutable instances. These factory methods are convenience factory methods to create a collection in less verbose and in concise way.Old way to create collectionsExampleimport java.util.Collections; import java.util.HashMap; import java.util.Map; public class Tester {    public static ... Read More

Externalization is used whenever we need to customize serialization mechanism. If a class implements an Externalizable interface then, object serialization will be done using writeExternal() method. Whereas at receiver's end when an Externalizable object is a reconstructed instance will be created using no argument constructor and then the readExternal() method ... Read More

Following are the notable differences between super() and this() methods in Java. super()this()Definitionsuper() - refers immediate parent class instance.this() - refers current class instance.InvokeCan be used to invoke immediate parent class method.Can be used to invoke current class method.Constructorsuper() acts as immediate parent class constructor and should be first line in ... Read More

Following are the notable differences between ArrayList and CopyOnWriteArrayList classes in Java. ArrayListCopyOnWriteArrayListSynchronizedArrayList is not synchronized.CopyOnWriteArrayList is synchronized.Thread SafeArrayList is not thread safe.CopyOnWriteArrayList is thread safe.Iterator typeArrayList iterator is fail-fast and ArrayList throws ConcurrentModificationException if concurrent modification happens during iteration.CopyOnWriteArrayList is fail-safe and it will never throw ConcurrentModificationException during iteration. The ... Read More

MySQL follows operator precedence and it has the following list of operators, having the same precedence which is on the same line −INTERVAL BINARY, COLLATE ! - (unary minus), ~ (unary bit inversion) ^ *, /, DIV, %, MOD -, + & | =, , >=, >,

When invoked with an integer argument, RAND( ) uses that value to seed the random number generator. Each time you seed the generator with a given value, RAND( ) will produce the same sequence of random numbers. Following example will demonstrate it −Examplemysql> Select RAND(1), RAND(1), Rand(1); +---------------------+---------------------+---------------------+ | RAND(1) ... Read More

As we know that NULL fails equality comparison with any value hence if the search string, provided in FIELD() function, is NULL then MySQL returns 0 as output.Examplemysql> Select FIELD(NULL,'Ram','is','good','boy'); +-------------------------------------+ | FIELD(NULL,'Ram','is','good','boy') | +-------------------------------------+ |                                   0 | +-------------------------------------+ 1 row in set (0.00 sec)

As we know that MySQL supports foreign key for referential integrity but it does not support CHECK constraint. But we can emulate them by using triggers. It can be illustrated with the help of an example given below −ExampleSuppose we have a table named ‘car1’ which can have the fix ... Read More

We can apply the PRIMARY KEY constraint to a column of an existing MySQL table with the help of ALTER TABLE statement. SyntaxALTER TABLE table_name MODIFY colum_name datatype PRIMARY KEY;                  OR ALTER TABLE table_name ADD PRIMARY KEY (colum_name); Suppose we have the following table ... Read More

Following is the required program.ExampleLive Demopublic class Tester {    static int factorial(int n) {       if (n == 0)          return 1;       else          return (n * factorial(n - 1));    }    public static void main(String args[]) {       int i, fact = 1;       int number = 5;       fact = factorial(number);       System.out.println(number + "! = " + fact);    } }Output5! = 120