JavaToPoint: September 2014

Arrays & Operators In Java

What is an Array

• An array is a block of consecutive memory
locations of the same data type.

• Individual locations are called array’s elements.

• Sometimes when we say “array’s element” we
mean the value stored in that element.

1.39 1.69 1 .74 0 .0 An array of doubles

Declaration of an Array

• There are two ways to declare an array:

anyType arrName [ ];

anyType [ ] arrName;

The difference becomes significant
only when several variables are
declared in one statement:

int [ ] a, b; // both a, b are arrays
int a [ ], b; // a is an array, b is not

Initialization (cont’d)

• An array can be declared an initialized in one
statement:

int scores [ ] = new int [10] ; // length 10

private double gasPrices [ ] = { 1.49, 1.69, 1.74 };

String words [ ] = new String [10000];

String cities [ ] = {"Atlanta", "Boston", "Cincinnati" };

Array’s Length

• The length of an array is determined when that
array is created.

• The length is either given explicitly or comes from
the length of the {…} initialization list.

• The length of an array arrName is referred to in
the code as arrName.length.

• length appears like a public field (not a method) in
an array object.

Two-Dimensional Arrays

• 2-D arrays are used to represent tables,
matrices, game boards, images, etc.

• An element of a 2-D array is addressed
using a pair of indices, “row” and “column.”

For example:

board [ r ] [ c ] = 'x';

2-D Arrays: Declaration

// 2-D array of char with 5 rows, 7 cols:

char letterGrid [ ] [ ] = new char [5][7];

// 2-D array of Color with 1024 rows, 768 cols:

Color image [ ] [ ] = new Color [1024][768];

// 2-D array of double with 2 rows and 3 cols:

double sample [ ] [ ] ={ { 0.0, 0.1, 0.2 },{ 1.0, 1.1, 1.2 } };

Operators in Java

• Arithmetic operators: + , - , * , / , %

• Increment and decrement operators: ++,--

• Relational Operators : <, >, <=, >=, !=, ==

• Bitwise Operators: <<, >>, &, |, ^, ~

• Logical Operators: &&, ||, !

• Assignment Operators : =

• Conditional or ternary operator: (condition) ? (if part)
: (else part)

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