Java Basics: Part1

Primitive Data Types (only types not passed by reference)

boolean

char: 16 bits

byte: 8 bit signed integer

short: 16 bit signed integer

int: 32 bit signed integer

long: 64 bit signed integer

float: 32 bit floating point

double: 64 bit floating point

C++ vs Java

Java uses packages

java.applet, java.io, java.net, java.util, java.awt

#include "strings.h" becomes
import java.lang.String

no unsigned integers

no operator overloading (can’t redefine +)

no struct, union, enum, typedef, or bitfields

all functions are virtual

no standalone functions (must be a method)

no explicit friend functions (everything in a package is a friend)

no multiple inheritance

restricted casting

0 != false and 0 != null

args[0] is not the program name

methods are defined within a class

Java Objects & Classes

implements (has interface only)

Definition: An interface is a named collection of method definitions (without implementations). An interface can also include constant declarations.

Interfaces can see public variables only

No Pointers: can’t find the address of anything

Objects are always passed by reference

Be careful of aliasing and when trying to copy

Non initialized objects are set to null

=, ==, clone(), and equals()

constructors are the same as C++ (use new)

no explicit destructors: Java uses garbage collection

instanceof function checks an object’s type

final

public, private, protected, package(default)