Core Java (All)

Introduction to Strings in Java

A String is a sequence of characters (e.g. "Hello World").

A String is an object in java, and not a primitive. 

 

Creating Strings

We can create a String object in two ways:

  1. Assigning a String literal to a String variable

    • e.g. String greeting = "Hello world!";

    • Here, "Hello world!" is a string literal.

My First JDBC Program

Prerequisites

1. Downloading, installing and configuring the database

See the installation and configuration note for your database.

2. Create table and insert data as:

Create table employee(empName varchar(20), id int PRIMARY KEY)

insert into employee values (‘name1’,1)

insert into employee values (‘name2’,2)

Path vs Classpath

The PATH environment variable contains a set of directories within the file system that the operating system uses to find executable files. When you type a command in command prompt, operating system will look for the corresponding executable in the current folder and then it will look inside every folder mentioned in the PATH environment variable in order. For instance, when you type javac, OS will search for java.exe within the current folder and then every folder mentioned inside in the PATH environment variable in order. [node:read-more:link]

Access Modifiers in Java

Access modifiers are used to specify the accessibility or access levels of a type (class, interface) and its members (methods, variables and even constructors). There are three access modifiers and four access levels in Java. The three access modifiers are are private, protected and public. Four access levels (from most restricted to least restricted) are private, default (no modifier), protected and public.  [node:read-more:link]

Constructors in Java

Constructors are used to initialize the state of an object when it is created. Constructors are invoked while creating objects, usually after the new keyword. A child class may also invoke a super constructor using the super keyword to initialize the parent object.

Constructors are similar in syntax to methods, but without any return type and have the same name as that of the class (case sensitive).

MyClass{

  MyClass(){

  }

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