Core Java || Java Introduction

Why should we learn programming languages?

computer can understand binary values only. 

computer can’t understand high level languages i.e., C++, Java... etc.

 

by using programming languages, we are writing code in human understandable language (English.) and then converting to machine understandable language that is binary values using compiler.

 

Note: in Java we are converting Java code (source code) into machine understandable language by using compiler, interpreter and JVM.

 

What is Java

Java is programming language by using Java we can develop standalone (desktop app), web applications…etc.!

 

How to develop Java Application

before work with Java first we should install Java software, download JDK and install Java in our computer.

1)write Java code, we can write Java code in notepad or editors like eclipse.

2)compile Java code by javac command

3)execute Java program by using java command.

How to Run/Execute Java Program?

save file with .java extension in note pad

Ex: Human.java

open command prompt in file location compile Java program by using this command

E:\>javac Human.java

.class file will be generated in that file location.

after compilation run Java program by using Java command.

E:\>java Human

here we use two commands to run and execute Java program.

1)javac

2)java

Javac (compiler) converts our Java code to byte code and executed byte code run by JVM in JRE by calling java command.

whenever we are compile and run our Java application we may get errors.

this errors are divided into 2 types.

1)Compile Time Error

2)Runtime Error

Compile time Error:

whenever we are compiling Java program using javac command entire source code compile at a time it verifies only syntax and misspelling of identifier and keywords.

Runtime Error:

after compilation successfully there may be chance of getting run time errors/ bugs. before hosting our application, we should find and handle these bugs.

this error may occur when user enter invalid inputs

example:  

divide number by zero, null values.

and file not found errors or logical errors, input/output errors …etc.