Comments

Documentation Comment Statement Comments
/**

*

*/

E.g.,

/**  This is a sample comment

*     that would span

*     multiple lines   */

//

// This is a sample single line comment

Primitive data Type

int

E.g., int sumOfNumbers;

double

E.g, double average;

char

E.g., char singleChar;

boolean

E.g., boolean isBig;

Declaring Variables

<Visibility>  <type>  <name>

E.g., private int sumOfNumbers

Note: Generally all field (i.e., class level) variables should be private

Print statements

Prints on the Same LinePrints on a new line
System.out.print(“”)

E.g., System.out.print(“The sum is: “ + sumOfNumbers);

System.out.println(“”)

Numeric Expressions

ExpressionMeaning
+Addition
Subtraction
*Multiplication
/Division
%Modulus division
+=

E.g., sum += value

This is the equivalent of

sum = sum + value

Rational Operators  – used in conditional statements (if, while, etc.)

Operator Meaning
= =equal
<less than
<=Less than or equal
>Greater than
>=Greater than or equal
!=Not equal

Conditional Controls

If – else if
if (condition){

statements

} else if (condition){

statements

}else{

statement

}

E.g., if ( sumOfNumbers > = 23) {

sumOfNumbers = 15;

totalSum += 23;

}else if (totalSum <156) {

System.out.println(“You don’t have enough money.”);

}else {

System.out.println(“You have just the right amount.”);

Loops

Do while statement For loop
do{

statements

}while (condition)

E.g., do  {

sum += value

} while (sum <= 456)

for (<initialization>; <condition>; <increment>) {

Statements

}

e.g., for ( int i = 0; i < = 10; i++) {

Statements

}

Scanner – to get user input

Meaning
import java.util.ScannerImports  scanner class
Scanner <name> = new Scanner(System.in)

E.g., Scanner userInput = new Scanner(System.in)

Declaring the Scanner
Variable = <name>.next<data>

E.g., number = userInput.nextInt( );

Using Scanner

Math Class

Meaning
import java.lang.MathImports  scanner class
Math.random( )

randomNumber = (int)(100*Math.random( ) + 1)

Creates a random number from 1 to 100
(high – low + 1 * Math.random( ) + low)Random number range
(int) Math.random

Or

(int) (high – low + 1 * Math.random( ) + low)

Makes the random numbers integers

Math.absAbsolute value of x: If x is negative, it returns the positive equivalent, otherwise it leaves it the same.

Arrays

Meaning
<type>[  <name>

int [ ] arrayVariable;

Declaring an array
<name> = new <type> [size of array]

arrayVariable = new int [25 ];

Allocate space for elements

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