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Transcript of 1 Programming Java Java Basics. 2 Java Program Java Application Program Application Program written...
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Programming Java
Java Basics
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Java ProgramJava Program Java Application Program
Application Program written in general programming languag
e
Applet Program running in Web Browser Environment Can be viewed by appletviewer or Web browser wi
th JVM
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Classes and ObjectsClasses and Objects Object
Memory Space to Define State and Operation Instance of Class
Class Template of Creating Object
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The Java Class LibrariesThe Java Class Libraries
java.applet : Applet related java.awt : Abstract Window Toolkit java.awt.event : Event process from awt component java.awt.image : Image processing java.beans : JavaBeans Component java.io : File or Network I/O Support java.lang : Java Language Support java.net : Network related functions java.util : Utility function
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Variables and AssignmentsVariables and Assignments
Variables Types
char 16bits Unicode character data boolean Boolean Variable byte 8 bits signed integer short 16 bits signed integer int 32 bits signed integer long 64 bits signed integer float 32 bits signed floating point number double 64 bits signed floating point number
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Primitive data typesPrimitive data types
Byte 8 -27 27-1
Short 16 -215 215-1
Int 32 -231 231-1
Long 64
Float 32
Double 64
Boolean 1 0 1
Char 16
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VariablesVariables
Variables: Name Type Value
Naming: May contain numbers,underscore,dollar sign,
or letters Can not start with number Can be any length Reserved keywords Case sensitive
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Variables and AssignmentsVariables and Assignments
int num = 100;
long m = 21234234L
double type : .5 0.8 9e-2 -9.3e-5
float type : 1.5e-3f;
Variable Declarationtype varName;
Value assignments
varName = value;
float x, y, x;
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Type Conversions in ExpressionType Conversions in Expression
char ch; int i; float f; double outcome;
ch = ‘0’; i = 10; f = 10.2f;
outcome = ch * i / f;
intfloat
double
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Type Conversions in AssignmentType Conversions in Assignment
Widening Conversion byte b = 127; int i; i = b; Narrowing Conversion byte b; int i = 258; b = (byte) i; Wrong Conversion byte b; int i = 127; b = i; Right Conversion (But data may be lost) byte b; int i = 127; b = (byte) i;
Type Casting
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AssignmentAssignment
= Example:int n;n = 10;orint n = 10; //same
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AssignmentAssignment
+= -= *= /= %=
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Arithmetic OperatorsArithmetic Operators
Operators + - * / % += -= *= /= %= ++ --
5 / 2 2 Why isn’t it 2.5 ?
5 % 2 1
4 / 2 2
4 % 2 0 count * num + 88 / val – 19 % count j += 6; j = j + 6;
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Boolean ExpressionsBoolean Expressions
boolean bb will be either true (1) or false (0)
Logical operations: !(not), && (and) || (or) boolean a,b;
a = true;b = false;System.out.println (“a && b is “ + (a && b));
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Relational OperatorsRelational Operators
== equality != inequality > greater than < less than >= greater than or equal to <= less than or equal to
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IncrementingIncrementing
Increment and Decrement i++ equivalent to i = i + 1; Can also do ++i, which uses i before incrementing
it. Decrementing: i--;
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The if - branching statementThe if - branching statement
if ( x < y) {x = y;}
if ( x < y ) {x = y;
}else { x = 88;}
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If/ElseIf/Else
if (logic condition) {something}else if (logic condition) { something}else {something else}
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Nested IFNested IF
if ( x < 0 ) {System.out.println( “ x is negative “ );}
else {if ( x > 0 ) {
System.out.println ( “x is positive” );}//end if x > 0else {System.out.println ( “x is zero “ );}
} //end else x >=0
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Switch/CaseSwitch/Case
Switch(variable){case(1): something;
break;case(23): something;
break;default: something;}
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CommentsComments
Single Line Comment int i = 10 ; // i is counter
Multiple Line Comment
/*
Some comments
*/ Documentation Comment
/**
Documentation Comment
*/
Using “javadoc” Tool,
make document
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Arrays ( One Dimensional)Arrays ( One Dimensional)
type VarName[]
Definition of One Dimensional Array
int ia[];
varName = new type[size]
Assign Range to One Dimensional Array
ia = new int[10];
type varName[] = new type[size]
Declaration of One Dimensional Array with Range
int ia[] = new int[10];
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Arrays ( One Dimensional)Arrays ( One Dimensional)
varName.length
Number of elements in Array
Type varName[] = {e0, … , en};
Initialization of One Dimensional Array
int j[] = {0, 1, 2, 3, 4, 5};
int k[];
K = j;
Example 1.15
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Arrays ( Arrays ( Multi-Multi-Dimensional)Dimensional)
type VarName[][];
Definition of Two Dimensional Array
float fa[][];
varName = new type[size1][size2];
Assign Range to Two Dimensional Array
fa = new float[2][3];
type varName[][] = new type[size1][size2];
Declaration of Two Dimensional Array with Range
float fa[] = new float[2][3];
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Arrays ( Arrays ( TwoTwo Dimensional) Dimensional)
varName.length
Number of elements in Multi-Dimensional Array
Type varName[][] = {{e00, … , e0n}, {e10,…,e1y}, {e20, …, e2z}};
Initialization of Multi-Dimensional Array
Example 1.16
varName[index].length
Number of elements in Each elements of Multi-Dimensional Array
Number of Raw
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Java KeywordsJava Keywords
50 Java Keywordsabstract double int superboolean else interface switchbreak extends long synchronizedbyte final native thiscase finally new throwcatch float package throwschar for private transient*class goto* protected tryconst* if public voidcontinue implements return volatiledefault import short whiledo instanceof static strictfp
assert (New in 1.5) enum (New in 1.5)The “assert” is recognized as keyword in JDK1.4 compiler, but we could not
use it.It can be used it from 1.5.
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First ApplicationFirst Application
/***Hello World, first application, only output.*/import java.io.*;
public class hello{ public static void main (String [] args) {
System.out.println(“Hello World\n”);} //end main
}//end class
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How to get it runningHow to get it running
Text in hello.java file Why?
To compile: javac hello.java
To run: java hello
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Notice:Notice:
Java is CASE SENSITIVE!! Whitespace is ignored by compiler Whitespace makes things easier to read…hence it
affects your grade File name has to be the same as class name in
file. Need to import necessary class definitions