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Java Articles
Page 304 of 450
Can 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 ...
Read MoreRead integers from console in Java
To read integers from console, use Scanner class.Scanner myInput = new Scanner( System.in );Allow a use to add an integer using the nextInt() method.System.out.print( "Enter first integer: " ); int a = myInput.nextInt();In the same way, take another input in a new variable.System.out.print( "Enter second integer: " ); Int b = myInput.nextInt();Let us see the complete example.Exampleimport java.util.Scanner; public class Demo { public static void main( String args[] ) { Scanner myInput = new Scanner( System.in ); int a; int b; int sum; System.out.print( ...
Read MoreCheck if the String contains only unicode letters or digits in Java
To check whether a String contains only unicode letters or digits in Java, we use the isLetterOrDigit() method and charAt() method with decision-making statements.The isLetterOrDigit(char ch) method determines whether the specific character (Unicode ch) is either a letter or a digit. It returns a boolean value, either true or false.Declaration −The java.lang.Character.isLetter() method is declared as follows −public static boolean isLetter(char ch)The charAt() method returns a character value at a given index. It belongs to the String class in Java. The index must be between 0 to length()-1.Declaration −The java.lang.String.charAt() method is declared as follows −public char charAt(int index)Let us ...
Read MoreCheck if the String contains only unicode letters in Java
In order to check if a String has only Unicode letters in Java, we use the isDigit() and charAt() methods with decision-making statements.The isLetter(int codePoint) method determines whether the specific character (Unicode codePoint) is a letter. It returns a boolean value, either true or false.Declaration −The java.lang.Character.isLetter() method is declared as follows −public static boolean isLetter(int codePoint)Here, the parameter codePoint represents the character to be checked.The charAt() method returns a character value at a given index. It belongs to the String class in Java. The index must be between 0 to length()-1.Declaration −The java.lang.String.charAt() method is declared as follows −public ...
Read MoreTimer Class in Java
The Timer Class in Java is a facility for threads to plan tasks for future execution in a background thread. Tasks may be executed a single time or multiple times. The Timer class is thread-safe i.e. the threads of the class do not require external synchronization and can share a single Timer object. A point to be noted is that all constructors start a Timer thread.The Timer Class in Java came into existence since JDK 1.3. This class ascends up to large numbers of concurrently scheduled tasks. Internally, it uses a binary heap in the memory to represent its task ...
Read MoreRemove all cancelled tasks from the timer's task queue in Java
One of the methods of the Timer class is the int purge() method. The purge() method removes all the canceled tasks from the timer’s task queue. Invoking this method does not affect the behavior of the timer, rather it eliminates references to the canceled tasks from the queue. The purge() method came into existence since JDK 1.5.The purge() method acts as a medium for space-time tradeoff where it trades time for space. More specifically, the time complexity of the method is proportional to n + c log n, where n is the number of tasks in the queue and c ...
Read MoreDoes JVM creates object of Main class in Java?
As we know that Java needs main() method to be static in the public class to make it executable. The prime reason for this requirement is to make JVM enable to call the main() method without creating an object. That simply means that JVM does not create the object of the Main class which contains the main() method. To justify the same, we can make the Main class containing the main method as abstract and program still runs.Following example showcases the same. Here we have made the main class abstract.Exampleabstract public class Tester { public static void main(String args[]) ...
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