Object-Oriented Programming with Java

Java Type Manipulation

ImanLHakim

Agenda

• What is Data • How Computer Stores Data • Java Data Type • Primitive Type • Primitive Data Conversion (Casting) • Arithmetic of Primitive Data • Wrapper Class of Primitive Data Type • Reference Type • Reference Type Casting • Object Class as Parents of all Java Classes • Immutable String and Mutable String • Basics String Operation and Regular Expression

What is Data

• The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data (plural of "datum") are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which information and then knowledge are derived. Raw data, i.e. unprocessed data, refers to a collection of numbers, characters, images or other outputs from devices that collect information to convert physical quantities into symbols. Wikipedia

• We use Computer to process data.

How Computer Stores Data

• Data stored in computer memory or storage in binary format.

• Computer only recognize binary type of data.

• It is Computer Programming Language and other programs that help us classified data into varieties type

Java Data Types

Typ

e

Reference

Class

Interface

Array

Primitive

Numeric

Floating Point

float (signed)

double (signed)

Integral

byte (signed)

short (signed)

int (signed)

long (signed)

char (unsigned)

Boolean

Return address

Integral Data Type

Data Type Value Default

Value Size Range

Char Unicode

character \u0000 16 bits \u0000 to \uFFFF

Byte Signed integer 0 8 bits -128 to 127

Short Signed integer 0 16 bits -32768 to 32767

Int Signed integer 0 32 bits -2147483648 to

2147483647

long Signed integer 0 64 bits

-9223372036854775808

to

9223372036854775807

Integral Literal IntegerLiteral: DecimalIntegerLiteral HexIntegerLiteral OctalIntegerLiteral DecimalIntegerLiteral: DecimalNumeral IntegerTypeSuffixopt HexIntegerLiteral: HexNumeral IntegerTypeSuffixopt OctalIntegerLiteral: OctalNumeral IntegerTypeSuffixopt IntegerTypeSuffix: one of l L DecimalNumeral: 0 NonZeroDigit Digitsopt Digits: Digit Digits Digit Digit: 0 NonZeroDigit NonZeroDigit: one of 1 2 3 4 5 6 7 8 9 HexNumeral: 0 x HexDigits 0 X HexDigits HexDigits: HexDigit HexDigit HexDigits HexDigit: one of

0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F OctalNumeral: 0 OctalDigits OctalDigits: OctalDigit OctalDigit OctalDigits OctalDigit: one of 0 1 2 3 4 5 6 7

Sample byte Literals

byte b1 = 015; byte b2 = 15; byte b3 = 0x15;

byte b4 = 0X15; byte b5 = -015; byte b6 = -15;

byte b7 = -0x15; byte b8 = -0X15;byte b9 = 127;

byte b10 = -128;

// byte b11 = 128;

//Type mismatch: cannot convert from int to byte

// byte b12 = -129;

//Type mismatch: cannot convert from int to byte

byte b13 = (byte) 128; // konversi tipe eksplisit

byte b14 = (byte) -129; // konversi tipe eksplisit

Sample short Literals

short s1 = 015; short s2 = 15; short s3 = 0x15;

short s4 = 0X15; short s5 = -015; short s6 = -15;

short s7 = -0x15; short s8 = -0X15; short s9 = 32767;

short s10 = -32768;

// short s11 = 32768; //Type mismatch: cannot

// convert from int to short

// short s12 = -32769; //Type mismatch: cannot

// convert from int to short

short s13 = (short) 32768; // konversi tipe eksplisit

short s14 = (short) -32768;// konversi tipe eksplisit

Sample int Literals

int i1 = 0555; int i2 = 555; int i3 = 0xFAfa; int i4 = 2147483647;

//int i5 = 2147483648;//The literal 2147483648 of type int is out of range

//int i6 = 2147483648L; //Type mismatch: cannot convert from long to int

int i7 = (int) 2147483648L; // konversi tipe eksplisit

int i8 = (int) 2147483649L; // konversi tipe eksplisit

int i9 = (int) 2147483650L; // konversi tipe eksplisit

int i10 = (int) 4294967294L;// konversi tipe eksplisit

int i11 = (int) 4294967295L;// konversi tipe eksplisit

int i12 = (int) 4294967296L;// konversi tipe eksplisit

int i13 = (int) 4294967297L;// konversi tipe eksplisit

int i14 = (int) 4294967298L;// konversi tipe eksplisit

int i15 = (int) 8589934593L;// konversi tipe eksplisit

Sample long Literals

long l1 = 0555;

long l2 = 555;

long l3 = 0xFAfa;

// long l4 = 2147483648;

//The literal 2147483648 of

// type int is out of range

long l5 = 2147483648L;

// long l6 = 9223372036854775808L; //The literal

// 9223372036854775808L of type long is out of range

Floating-Point Data type

Type Contains Default Size Range

Float IEEE 754

floating point 0.0 32 bits

1.4E-45 to

3.4028235E+3

8

double IEEE 754

floating point 0.0 64 bits

4.9E-324 to

1.7976931348

623157E+308

Float Literal FloatingPointLiteral: DecimalFloatingPointLiteral HexadecimalFloatingPointLiteral DecimalFloatingPointLiteral: Digits . Digitsopt ExponentPartopt FloatTypeSuffixopt . Digits ExponentPartopt FloatTypeSuffixopt Digits ExponentPart FloatTypeSuffixopt Digits ExponentPartopt FloatTypeSuffix ExponentPart: ExponentIndicator SignedInteger ExponentIndicator: one of e E SignedInteger: Signopt Digits Sign: one of + - FloatTypeSuffix: one of f F d D HexadecimalFloatingPointLiteral: HexSignificand BinaryExponent FloatTypeSuffixopt HexSignificand: HexNumeral HexNumeral . 0x HexDigitsopt . HexDigits 0X HexDigitsopt . HexDigits BinaryExponent: BinaryExponentIndicator SignedInteger BinaryExponentIndicator:one of p P

Sample float Literals

float f1 = 1e1f; float f2 = 2.f;

float f3 = .3f;

float f4 = 0f; float f5 = 3.14f;

float f6 = 6.022137e+23f;

//float f7 = .394;/* ^Type mismatch:

cannot convert from double to float*/

float f8 = 0xfff;//last f for float

float f9=0Xf.aP1F;/*(15+10/16ths)*

2^1= 31.25 */

Sample double Literals

double d1 = 0XaP0; // 10 * 2^0 = 10

double d2 = 0XfP2D; // 15 * 2^2 = 60

//double d3 = .98P2;

/* ^Syntax error on token "P2", delete

this token*/

double d4 = 'x';

//implisit conversion char -> double

double d5 = 232;

//implisit conversion int -> double

char Literal

Seq Keterangan

\n Newline (\u000A)

\t Tab (\u0009)

\b Backspace (\u0008)

\r Return (\u000D)

\f Form feed (\u000C)

\\ Backslash itself (\u005C)

\' Single quote (\u0027)

\" Double quote (\u0022)

\ddd Sebuah karakter ASCII, dimana setiap d diganti dengan angka oktal antara 0-

377, jumlah angka oktal tidak mesti 3. contoh ‘\62’, ‘\134’

\uxxx

x

Sebuah karakter Unicode, dimana setiap x diganti angka hexadesimal, jumlah

angka hexadesimal harus selalu 4. contoh ‘\x0012’, ‘\xBAba’.

CharacterLiteral: ' SingleCharacter ' ' EscapeSequence ' SingleCharacter: InputCharacter but not ' or \

Sample char Literal

char c1 = 'a'; char c2 = '2';

// char c3 = '76'; //Invalid character constant

// char c4 = '''; //Invalid character constant

char c5 = '\'';

// char c6 = '\'; //Invalid character constant

char c7 = '\76';

// char c8 = '\U0032';//Invalid escape sequence

// (valid ones are \b \t \n \f \r \" \' \\ )

char c9 = '\u0032'; char c10 = '\10';

char c11 = '\u20AC';

char c12 = '\377'; char c13 = '\uffff';

boolean Literal

• boolean only have true and false

• Unlike C/C++, java does not have boolean literal 1 or 0 (zero).

Java Operators

Precedence Operator Description Association

1 ++,-- Postincrement, Postdecremet R L

2 ++,-- Preincrement, Predecrement R L

+,- Unary plus, unary minus R L

~ Bitwise compliment R L

! Boolean NOT R L

3 New Create object R L

(type) Type cast R L

4 *,/,% Multiplication, division, remainder L R

5 +,- Addition, subtraction L R

+ String concatenation L R

6 <<, >>, >>> Left shift, right shift, unsigned right shift L R

7 <, <=, >, >= Less than, less than or equal to, greater than, greater

than or equal to L R

Instanceof Type comparison L R

Java Operators (cont…)

Precedence Operator Description Association

8 ==, != Value equality and inequality L R

==, != Reference equality and inequality L R

9 & Boolean AND L R

& Bitwise AND L R

10 ^ Boolean XOR L R

^ Bitwise XOR L R

11 | Boolean OR L R

| Bitwise OR L R

12 && Conditional AND L R

13 || Conditional OR L R

14 ?: Conditional Ternary Operator L R

15

=,+=,-=, *=,/

=,%=,&=,^=, |=,

<<=, >> =, >>>=

Assignment Operators R L

Exercise

• Create sample java code that use all operator above except “Create object”, “Type Cast”, “Object Comparation”

Primitive Data Convertion

Convert Convert to:

from: boolean byte short char int long float double

boolean - N N N N N N N

byte N - Y C Y Y Y Y

short N C - C Y Y Y Y

char N C C - Y Y Y Y

int N C C C - Y Y* Y

long N C C C C - Y* Y*

float N C C C C C - Y

double N C C C C C C -

Wrapper Class of primitives

• Each primitive type has wrapper class • Each class has fields and method to ease data manipulation • Since JDK 1.5 between primitive and wrapper converted

automatically, these call auto boxing (primitive wrapper), auto unboxing ( wrapper primitive)

Primitive Wrapper class

boolean java.lang.Boolean

char java.lang.Character

byte java.lang.Byte

short java.lang.Short

int java.lang.Integer

long java.lang.Long

float java.lang.Float

double java.lang.Double

Common Used Methods of Wrapper Class

• Y. xValue()Returns the x value of this y object. • Y.parseX(String s)Returns a new X initialized to

the value represented by the specified String s. • Y.valueOf(X x) Returns a Y instance

representing the specified x value. • Y.toXString()Returns a string representation of

the integer argument as an unsigned integer in base X.

• Y.toString()Returns a string representation of this Y object.

Common Used Fields of Wrapper Class

• X.MAX_VALUE maximal value of type X

• X.MIN_VALUE minimal value of type X

• D.NaN A constant holding a Not-a-Number (NaN) value of type D (Double or Float).

Simplified Memory Layout of Primitive Reference Type

float pi = 3.1415926 ; Student s1 = new Student(“iman”, 19); Student s2 = new Student(“Angust”, 14);

V -Table

Student

pi = 3.1415926

s1

s2

Student

SCHOOL=“ITT”

Class definition and static member value

public class Student{ public static String SCHOOL = “IIT”; public String name; public int age; public Student (String name, String age){ this.name = name; this.age = age } }

s2

name = “Angust”

age = 14

s1

name = “iman”

age = 19

Type Casting

• Let an object with type X acts as object with Type Y. • Java understands two types of casting

– Implicit or up casting , done automatically – Explicit or down casting, done manually

//let’s say X is abstract class X x1 = new Y();//implicit (up) casting YX X x2 = new Z();//implicit (up) casting Z X Y y1 = new Y(); Z z1 = new Z(); Y y2 = (Y) x1;//explicit (down) casting XY Z z2 = (Z) x2;//explicit (down) casting ZZ

Introducing java.lang.Object Class

• Class java.lang.Object is the root of the class hierarchy. Every class has Object as a superclass. All objects, including arrays, implement the methods of this class.

• Some of java.lang.Object’s methods highly recommended to be implemented by its descendent.

Important java.lang.Object’s Methods

Return Type Method Signature

protected Object clone() Creates and returns a copy of this object.

boolean equals(Object obj) Indicates whether some other object is "equal to" this one.

int hashCode() Returns a hash code value for the object.

String toString() Returns a string representation of the object.

Class<?> getClass() Returns the runtime class of this Object.

Copying Object

Shallow copy

X x1 = new X();

X x2 = x1;//copy x1x2;

x1 == x2;//true

x1.getClass() ==

x2.getClass(); //true

Deep copy (clone)

X x1 = new X();

X x2= x1.clone();//copy xx2;

x1 != x2;//true

x1.getClass() ==

x2.getClass(); //true

See Item 11: Override clone judiciously of Bloch, Joshua (2008), Effective Java (2 ed.), Addison-Wesley.

Comparing Objects

• Use equals() method to compare reference type, don’t use == operator. • Implement equals() method on every class that it’s instances not (object)

always unique, or may compared. • The equals method implements an equivalence relation. It is:

– Reflexive: For any non-null reference value x, x.equals(x) must return true. – Symmetric: For any non-null reference values x and y, x.equals(y) must return

true if and only if y.equals(x) returns true. – Transitive: For any non-null reference values x, y, z, if x.equals(y) returns true

and y.equals(z) returns true, then x.equals(z) must return true. – Consistent: For any non-null reference values x and y, multiple invocations of

x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.

– For any non-null reference value x, x.equals(null) must return false.

• Always override hashCode() when you override equals. ~ Bloch, Joshua (2008), Effective Java (2 ed.), Addison-Wesley.

Make Object Easy to Observe

• Implement toString to make your class much

more pleasant to use.

• The toString method is automatically invoked

when an object is passed to println, printf, the

string concatenation operator, or assert, or

printed by a debugger.

String

• The String class represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class.

• Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings.

• The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for extracting substrings, and for creating a copy of a string with all characters translated to uppercase or to lowercase. Case mapping is based on the Unicode Standard version specified by the Character class.

• The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuilder(or StringBuffer) class and its append method.

Regular Expresion

• In computing, a regular expression, also referred to as regex or regexp, provides a concise and flexible means for matching strings of text, such as particular characters, words, or patterns of characters. A regular expression is written in a formal language that can be interpreted by a regular expression processor, a program that either serves as a parser generator or examines text and identifies parts that match the provided specification. ~ wikipedia

Regex in Java

• Since Java 1.4 we can perform textual pattern matching with regex. • Java provides Pattern and Matcher classes of the java.util.regex

package. • String class has some regex methods below

Return Type Method Signature

boolean matches(String regex) Tells whether or not this string matches the given regular expression.

String replaceAll(String regex, String replacement) Replaces each substring of this string that matches the given regular expression with the given replacement.

String replaceFirst(String regex, String replacement) Replaces the first substring of this string that matches the given regular expression with the given replacement.

String[] split(String regex) Splits this string around matches of the given regular expression.

String[] split(String regex, int limit) Splits this string around matches of the given regular expression.

Assignment

• Create Text Base Reverse Polish notation (RPN) Calculator Application with addition, subtraction, multiplication and division operators.

and Remember…..