Lecture An introduction to computer science using java (2nd Edition): Chapter 3 - S.N. Kamin, D. Mickunas, E. Reingold

Chapter 3 - Fundamental data types of Java. In this chapter we will: Discuss four important data types: integers, real numbers, strings, characters; describe the process of developing and debugging a Java program.

Chapter 3

Fundamental Data Types of Java

Lecture Slides to Accompany

An Introduction to Computer Science

Using Java (2nd Edition)

byS.N Kamin, D Mickunas, E Reingold

Chapter Preview

In this chapter we will:

• discuss four important data types

Integer Arithmetic Operations

Symbol Operation Example

Precedence Rules

1 Evaluate all subexpressions in parentheses

2 Evaluate nested parentheses from the

inside out

3 In the absence of parenthes e s or within

parenthes e s

a Evaluate *, /, or % before + or –

b Evaluate sequences of *, /, and % operators

from left to right

c Evaluate sequences of + and – operators from

left to right

Real Arithmetic Operations

Symbol Operation Example

+ Addition 4.50e01 + 5.30e00 =

4.8e00

String Method Examples

OutputBox out = new OutputBox();

String s1 = “Here is a test string”;

out.println(s1.indexOf(“s”)); // prints 6out.println(s1.indexOf(“x”)); // prints -1

out.println(s1.length()); // prints 22

out.println(s1.substring(8,14));

// prints ‘a test’

Characters

• Any key you type on the keyboard generates

a character which may or may not be

displayed on the screen (e.g nonprinting

Important Literal Characters

‘A’, … ,‘Z’ Uppercase letters

‘a’, … ,‘z’ Lowercase letters

Common Debugging Problems

• Misleading compiler error messages

– Syntax errors indicated on one-line may actually reflect an error made on an earlier line

Limitations of Numeric Variables

• Unlike the integers mathematics the type int

is not infinitely large and it is possible to

compute a value incorrectly because the

value is too large to be stored in an int

variable storage location

• Unlike the real numbers in mathematics the

type double is not dense, it is not always

possible to test double expressions for

equality and obtain a correct result due to

rounding errors in representations

Mixing Numeric Data Types

• Java will automatically convert int expressions to double values without loss of information

int i = 5;

double x = i + 10.5;

• To convert double expressions to int requires a

typecasting operation and truncation will occur

i = (int) (10.3 * x)

• To round-up instead of truncating add 0.5

i = (int) (10.3 * x + 0.5)

Characters as Integers

• It is legal to assign a char to an int variable

int i = ‘a’; // assigns 97 to i

• It is legal to assign a n int to an char

variable

char c = 97; // assigns ‘a’ to c

• It is possible to perform arithmetic on char variables

char ch = ‘a’;

ch = ch + 1; // assigns ‘b’ to ch