Introduction to Java

CST200 – Week 1: Introduction to Java

Instructor: Andreea Molnar

Outline

•Aims

•Basic Concepts

•Strings

•Arrays

Aim

•The aim of this presentation is to emphasis on some of the material covered by the pluralsigh videos.

Basic Concepts

•Expression: see more about them here: http://www.d.umn.edu/~gshute/java/statements.html

•Algorithm: see a definition here: http://en.wikipedia.org/wiki/Algorithm

Strings and Arrays

The first letter of a String is at the position 0 and the first value of an array is at the position 0.

Strings

Any sequence of characters, for example:

String s = “Arizona”;

String s = “1457 Mesa”;

String s = “@u”;

Strings - Methods

You can find all the String methods at: http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

Strings - Methods

public int length() – returns the length of the string

String s = “CST 200”;

s.length() – will return 7 as there are 7 characters in the string

Strings - Methods

public int length() – returns the length of the string

String s = “CST 200”;

s.length() – will return 7 as there are 7 characters in the string (space is count as a separate character)

Strings - Methods

public char charAt(int index)– returns the character value at the specified index

String s = “CST 200”;

C S T 2 0 0

00 1 2 3 4 5 6

index

Strings - Methods

public char charAt(int index)– returns the character value at the specified index

String s = “CST 200”;

C S T 2 0 0

00 1 2 3 4 5 6

The first character of a String is at the position 0!!!

Strings - Methods

String s = “CST 200”;C S T 2 0 0

00 1 2 3 4 5 6

System.out.println(s.charAt(0));//will print C

System.out.println(s.charAt(6));//will print 0

Strings - Methods

public int indexOf(String str) - returns the index within this string of the first occurrence of the specified substring

String s = “CST 200”;

C S T 2 0 0

00 1 2 3 4 5 6

System.out.println(s.indexOf(“T”));

//will print 3

Arrays

Array is a container that holds a fixed number of values.

int[] array = {10, 20, 30, 50};

10 20 30 50

0 2 3 4

index

Arraysint[] array = {10, 20, 30, 50};

10 20 30 50

0 1 2 3

To print the values of this array:

System.out.println(array[0]);//will print 10

System.out.println(array[1]);//will print 20

System.out.println(array[2]);//will print 30

System.out.println(array[3]);//will print 50

Summary

•Expression definition

•Algorithm definition

•The first character of an array starts at position 0

•The first element of an array starts at the position 0