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Object Oriented Programming Articles
Page 447 of 589
Is there any alternative solution for static constructor in java?
The main purpose of constructors in Java is to initialize the instance variables of a class.But, if a class have Static variables you cannot initialize them using the constructors (you can assign values to static variables in constructors but in that scenario, we are just assigning values to static variables). because static variables are loaded into the memory before instantiation (i.e. before constructors are invoked)So, we should initialize static variables from static context. We cannot use static before constructors, Therefore, as an alternation to you can use static blocks to initialize static variables.Static blockA static block is a block of ...
Read MoreHow to insert data into a table with auto-incremented columns using JDBC?
While inserting data into a table with auto-incremented column, just leave that particular column out and insert remaining values by specifying the remaining columns using the following syntax of the INSERT statement −INSERT into table_name (column_name1, column_name2....) values(value1, value2....)ExampleLet us create a table with name sales in MySQL database, with one of the columns as auto-incremented, using CREATE statement as shown below −CREATE TABLE Sales( ID INT PRIMARY KEY AUTO_INCREMENT, ProductName VARCHAR (20), CustomerName VARCHAR (20), DispatchDate date, DeliveryTime time, Price INT, Location VARCHAR(20) );Following JDBC program establishes a connection with the database ...
Read MoreHow to retrieve auto-incremented value generated by PreparedStatement using JDBC?
While creating a table, in certain scenarios, we need values to column such as ID, to be generated/incremented automatically. Various databases support this feature in different ways.In MySQL database you can declare a column auto increment using the following syntax.CREATE TABLE table_name( ID INT PRIMARY KEY AUTO_INCREMENT, column_name1 data_type1, column_name2 data_type2, column_name3 data_type3, column_name4 data_type4, ............ ........... );While inserting records in a table there is no need to insert value under the auto-incremented column. These will be generated automatically.For example, in a table if we have a column with name ID and data type ...
Read MoreHow to create a table with auto-increment column in MySQL using JDBC?
While creating a table, in certain scenarios, we need values to column such as ID, to be generated/incremented automatically. Various databases support this feature in different ways.In MySQL database you can declare a column auto increment using the following syntax.CREATE TABLE table_name( ID INT PRIMARY KEY AUTO_INCREMENT, column_name1 data_type1, column_name2 data_type2, column_name3 data_type3, column_name4 data_type4, ............ ........... );MySQL query to create a table with auto-incremented column.CREATE TABLE Sales( ID INT PRIMARY KEY AUTO_INCREMENT, ProductName VARCHAR (20) NOT NULL, CustomerName VARCHAR (20) NOT NULL, DispatchDate date, DeliveryTime timestamp, Price ...
Read MoreCan 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 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 ...
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