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 Line | Prints on a new line |
| System.out.print(“”)
E.g., System.out.print(“The sum is: “ + sumOfNumbers); |
System.out.println(“”) |
Numeric Expressions
| Expression | Meaning |
| + | 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.Scanner | Imports 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.Math | Imports 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.abs | Absolute 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 |
