Ultimate Java Programming Cheatsheet

Java Programming Cheatsheet

Java is one of the most popular, most adopted and general purpose programming language used by millions of developers and billions of devices around the world. It is a class-based, object-oriented language and designed to be portable, which means that you can find it on all platforms, operating systems, and devices. It is used to develop all kinds of Android apps, desktop apps, and video games. It is also commonly used as a server-side language for enterprise-level back end development. This programming language has long-term compatibility and developers are comfortable with Java.

Cheat-sheet for Java Programming is given below:

Java Data Types

Data type specifies the size and type of values that can be stored in an identifier. The Java language is rich in its data types. Different data types allow you to select the type appropriate to the needs of the application.

Data types in Java are classified into two types:

Primitive—which include Integer, Character, Boolean, and Floating Point.

Non-primitive—which include Classes, Interfaces, and Arrays.

byte / short / int / long	10,-30
float / double	88.58
char	‘D’
boolean	true, false
String	“­Keep Following Techworm”

Java Data Conver­sions

String to Number int i = Intege­r.p­ars­eIn­t(­str); double d = Double.pa­rse­Dou­ble­(s­tr);

Any Type to String String s = String.va­lue­Of(­va­lue);

Numeric Conver­sions int i = (int)

Java Arithmetic Operators

x + y	add	x – y	subtract
x * y	multiply	x / y	divide
x % y	modulus	++x / x++	increment
		–x / x–	decrement

Java Comparison Operators

x < y	Less	x <= y	Less or eq
x > y	Greater	x >= y	Greater or eq
x == y	Equal	x != y	Not equal

Java Boolean Operators

! x (not)

x && y (and)

x || y (or)

Java Text Formatting

printf style format­ting System.ou­t.p­rin­tf(­”­Count is %d\n”, count); s = String.fo­rma­t(“Count is %d”, count);Mess­age­Format style format­ting s = Messag­eFo­rma­t.f­ormat(  ­”At {1,time}, {0} Runs Scored.”,  25, new Date());Indi­vidual Numbers and Dates s = Number­For­mat.ge­tCu­rre­ncy­()  .fo­rma­t(x); s = new Simple­Dat­eFo­rma­t(“”yyyy/mm/dd””)  .fo­rma­t(new Date());

Java Hello World

public class HelloWorld { public static void main(String[] args) { System.out.println("Hello, World"); } }

Java String Methods

s.le­ngth()	length of s
s.ch­arA­t(i)	extract ith character
s.su­bst­rin­g(­start, end)	substring from start to end-1
s.to­Upp­erC­ase()	returns copy of s in ALL CAPS
s.to­Low­erC­ase()	returns copy of s in lowercase
s.in­dex­Of(x)	index of first occurence of x
s.re­pla­ce(­old, new)	search and replace
s.sp­lit­(r­egex)	splits string into tokens
s.trim()	trims surrou­nding whitespace
s.eq­ual­s(s2)	true if s equals s2
s.co­mpa­reT­o(s2)	0 if equal/+ if s > s2/- if s < s2

Java Statements

If Statem­ent if ( expre­ssion ) {  ­st­ate­ments } else if ( expre­ssion ) {  ­st­ate­ments } else {  ­st­ate­ments }While Loop while ( expre­ssion ) {  ­st­ate­ments }Do-While Loop do {  ­st­ate­ments } while ( expre­ssion );For Loop for ( int i = 0; i < max; ++i) {  ­st­ate­ments }For Each Loop for ( var : colle­ction ) {  ­st­ate­ments }Switch Statem­ent switch ( expre­ssion ) {  case value:  ­ ­ ­st­ate­ments  ­ ­ ­break;  case value2:  ­ ­ ­st­ate­ments  ­ ­ ­break;  ­def­ault:  ­ ­ ­st­ate­ments }Exce­ption Handling try {  ­sta­tem­ents; } catch (Exce­pti­onType e1) {  ­sta­tem­ents; } catch (Exception e2) {  ­cat­ch-all statem­ents; } finally {  ­sta­tem­ents; }

Applications of Java

Java is being used in:

1. Real-time Systems
2. Simulation and Modelling
3. object oriented Databases
4. Artificial Intelligence and Expert Systems
5. CIM/CAD/CAM Systems
6. Neural Networks and Parallel Programming
7. Decision Support Systems