MSA Java (rp) Cheat Sheet

A Programming › Java cheat sheet in English by rawbeef

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PRs

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Data Types

String	" type string here "
int	E.G: 0
boolean	true/false
char	'x'
double	E.G 0.00

Operators (Summary)

+	Addition / String concatenation
%	Modulus (remainder)
++ , --	Increment / Decrement by 1
!	Inverts boolean value
= , ==	Assigns, Equals to
!=	Does Not equal to
>=	Greater than OR Equal to
<=	Lesser than OR Equal to
&&	Conditional - AND
\|\|	Conditional - OR

Methods

System.out.println(line)

System.out.printf(format, arguments)

Helper.readDataType(string)

// For printf formatting //
%d = integer
%s = String
%f = double (.2f = 2dp)
%b = boolean

Loops / Impt Statements

while(condition)	(option != 4) { code }
for(var,cond,incre)	(int 1=0;i<10;i++)
if / else if / else	if(condition) { code }
switch(Expression)	switch (choice)

Switch syntax: E.g: Input is an int Choice

Switch (choice)
{
case 1:
< code >
break;
.....
default:
< code >
break;
}

Arrays

Declaring an Array
Syntax:
Datatype[ ] nameOfArray =
new Datatype[ No. of elements in array ];

Example:
int [ ] randomValues = new int [ 7 ];
// Creates an array called randomValues with 7 elements (0-6)

Assigning Value to Array: (Using prev E.G)
randomValues[3] = 100;
// Assigns value of 100 to the 4th element [3] of randomValues array

Declaring & Initializing @ Same Time
int[ ] randomValues = {5,12,51,23,12,24,21};
// Creates an array called randomValues and assigning 7 elements in it in a single line.

Accessing Elements:
System.out.println(randomValue[3]);
// Prints out "23" (prev example)

Finding out Array Length
System.out.println(randomValue.length);
// Prints out 7

Values for Primitive Arrays

int	0
double	0.0
boolean	false
String	null

String Methods

charAt(index)	Returns char @ index
endsWith(suffix)	if ends w suffix
equalsIgnoreCase(string)
length()	Returns length of string
startsWith(prefix)	if starts w prefix
toUpperCase()	Converts to upperCase
toLowerCase()	Converts to lowerCase

Class Diagram

'+' = Public , '-' = Private
underlined = Static

// Constructors have the same name as class.
// if return type is 'void' , no return statement is required.

Creation of Class

// Using the Class Diagram above //
Declare Fields First:
public String licenseNo, colour;
public int speed;

Constructor
[Right-click, Source, Create constructor using Fields, delete the super(); ]

Create Methods:
public void accelerate(int acc)
{
}

public void honk ()
{
}

// Creating Array/ Object in Main Class //

Array:
Syntax:
ClassName[ ]arrayName = new ClassName[x];

E.g:
Car[ ] testArray = new Car[5]

Objects
E.g:
Car newObject = new Car();
// Creates a new object, called 'newObject'.

Calling a method in Main class from another class
newObject.methodName();

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