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;
}
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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 |
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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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Created By
Metadata
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