May 20th - 2011

Reading: Section 5.7 pages 209-214
first few sections of chap. 5 Classes

Review

Basic Data Types

Integer:

byte :1byte
short : 2bytes
int : 4bytes
long : 8bytes

Floating Point Values: (IEEE 754)

float : 4bytes +-3.4 * 10^38 to 7 digit decimal
double: 8bytes +-1.7 * 10^308 to 15 digit decimal

Char:

for characters
each 2 byte Unicode

12:41

Boolean:

Two values: true, False
size is implementation- dependent
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Conversion Between Data Types

widening conversion: does not risk loss of information
narrowing conversion : does risk loss of information

conversion from a signed byte/short to char

12:53

booleans not convertable

narow -> big to small
widening conversion -> small to big

12:57

byte --> smallIt
long -->bigInt

big Int = smallInt // widening-ok

if i want to write:
smallInt = bigInt; //narrowing error
smallInt(byte) BigInt; // narrowing w/
// explicitcast - OK

1:03

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Assignment conversion: conversion to match right-hand data type to left hand
bigInt = Smallint converts smallInt to bigInt

casting: explicit conversion specified by the programmer

Promotion: when evaluating expressions, the java compiler tries to make bothoperands be the same dara tyoe using widening conversions.
int a, b;
float c,d;
a = 3
b = 4
c = (a/b); --> zero
d= ((float)a)/b) --> 0.75

long a;
float b;

c = a+ b
1:14

Arrays

Many instances of a single basic types.

- Strings are arrays of characters
- Grocery bill is an array of numbers

Java provides arrays as a basic part of the language

-indexed from 0
- all entries are of the same type
- space required for n items of size k is n*k
- indexed by entry
byte[] = arrayeofbyte[5] ;

1:20

diagrams