• Most people are familiar with Java as a language for Internet applications

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Chapter 1

Getting Started

Introduction To Java Introduction To Java

l f ili i h

• Most people are familiar with Java as a language for Internet applications

• We will study Java as a general purpose programming language

p g g g g

– The syntax of expressions and assignments will be similar to that of other high‐level languages g g g

– Details concerning the handling of strings and console output will probably be new p p y

Origins of the Java Language Origins of the Java Language

• Created by Sun Microsystems team led by James Gosling (1991)

• Originally designed for programming home appliances

– Difficult task because appliances are controlled by a wide variety of computer processors

– Team developed a two‐step translation process to simplify the task of compiler writing for each class of appliances

Origins of the Java Language Origins of the Java Language

• Significance of Java translation process

– Writing a compiler (translation program) for each type of appliance processor would have been very costly

– Instead, developed intermediate language that is the same

f ll t f J b t d

for all types of processors : Java byte‐code

– Therefore, only a small, easy to write program was needed to translate byte code into the machine code for each to translate byte‐code into the machine code for each processor

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Origins of the Java Language Origins of the Java Language

P t i k N ht d J th P t S

• Patrick Naughton and Jonathan Payne at Sun

Microsystems developed a Web browser that could run programs over the Internet (1994)

run programs over the Internet (1994)

– Beginning of Java's connection to the Internet – Original browser evolves into HotJava

• Netscape made its Web browser capable of running Java programs (1995)

Oth i f ll it

– Other companies follow suit

Objects and Methods Objects and Methods

• Java is an object‐oriented programming (OOP) language g g

– Programming methodology that views a program as consisting of objects that interact with one as consisting of objects that interact with one another by means of actions (called methods) Objects of the same kind are said to have the – Objects of the same kind are said to have the

same type or be in the same class

Terminology Comparisons Terminology Comparisons

• Other high‐level languages have constructs called procedures, methods, functions, and/or p subprograms

– These types of constructs are called methods in – These types of constructs are called methods in

Java

All i t t i J i l di

– All programming constructs in Java, including methods, are part of a class

Java Application Programs Java Application Programs

Th f J li i

• There are two types of Java programs: applications and applets

A J li i " l " J

• A Java application program or "regular" Java program is a class with a method named main

Wh J li ti i th ti

– When a Java application program is run, the run‐time system automatically invokes the method named main – All Java application programs start with theAll Java application programs start with the mainmainmethodmethod

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Applets Applets

A J l (li l J li i ) i J

• A Java applet (little Java application) is a Java

program that is meant to be run from a Web browser

C b f l ti th I t t

– Can be run from a location on the Internet

– Can also be run with an applet viewer program for debugging

debugging

– Applets always use a windowing interface

• In contrast application programs may use a In contrast, application programs may use a windowing interface or console (i.e., text) I/O

A Sample Java Application Program A Sample Java Application Program

System out println System.out.println

• Java programs work by having things called objects perform actions j p

– System.out: an object used for sending output to the screen

to the screen

• The actions performed by an object are called h d

methods

– println: the method or action that the System.out object performs

System out println System.out.println

• Invoking or calling a method: When an object performs an action using a method

– Also called sending a message to the object

– Method invocation syntax (in order): an object,a dot (period), the method name, and a pair of parentheses – Arguments: Zero or more pieces of information needed by

th th d th t l d i id th th

the method that are placed inside the parentheses

System.out.println("This is an argument");

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Variable declarations Variable declarations

• Variable declarations in Java are similar to those in other programming languages p g g g g

– Simply give the type of the variable followed by its name and a semicolon

name and a semicolon

int answer;

Using = and + Using = and +

• In Java, the equal sign ( = ) is used as the assignment operator

– The variable on the left side of the assignment operator is assigned the value of the expression on the right side of

th i t t

the assignment operator

answer = 2 + 2;

h l i ( ) b d d

• In Java, the plus sign (+) can be used to denote addition (as above) or concatenation

– Using +, two strings can be connected together

System.out.println("2 plus 2 is " + answer);

Computer Language Levels Computer Language Levels

Hi h l l l A l th t l d it

• High‐level language: A language that people can read, write, and understand

– A program written in a high‐level language must be translated into a

l th t b d t d b t b f it b

language that can be understood by a computer before it can be run

• Machine language: A language that a computer can understand

• Low‐level language: Machine language or any language similar to machine language

• Compiler: A program that translates a high level language

• Compiler: A program that translates a high‐level language program into an equivalent low‐level language program

– This translation process is called compiling

Byte Code and the Java Virtual Machine Byte‐Code and the Java Virtual Machine

Th il f i l l

• The compilers for most programming languages translate high‐level programs directly into the machine language for a particular computer

p p

– Since different computers have different machine languages, a different compiler is needed for each one

• In contrast the Java compiler translates Java programs into

• In contrast, the Java compiler translates Java programs into byte‐code, a machine language for a fictitious computer called the Java Virtual Machine

– Once compiled to byte‐code, a Java program can be used on any computer, making it very portable

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Byte Code and the Java Virtual Machine Byte‐Code and the Java Virtual Machine

I Th h l

• Interpreter: The program that translates a program written in Java byte‐code into the machine language for a particular computer when a Java program is for a particular computer when a Java program is executed

– The interpreter translates and immediately executes each – The interpreter translates and immediately executes each

byte‐code instruction, one after another

– Translating byte‐code into machine code is relatively easy g y y y compared to the initial compilation step

Program terminology Program terminology

C d A t f

• Code: A program or a part of a program

• Source code (or source program): A program written in a high‐level language such as Java

in a high‐level language such as Java

– The input to the compiler program

• Object code: The translated low‐level program Object code: The translated low level program

– The output from the compiler program, e.g., Java byte‐

code

– In the case of Java byte‐code, the input to the Java byte‐

code interpreter

Class Loader Class Loader

• Java programs are divided into smaller parts called classes

– Each class definition is normally in a separate file and compiled separately

• Class Loader: A program that connects the byte‐

code of the classes needed to run a Java program

– In other programming languages, the corresponding program is called a linker

Compiling a Java Program or Class Compiling a Java Program or Class

E h l d fi i i b i fil h i h

• Each class definition must be in a file whose name is the same as the class name followed by .java

– The class FirstPrograme c ass st og a must be in a file named ust be a e a ed FirstProgram.java

• Each class is compiled with the command javacfollowed by the name of the file in which the class resides

the name of the file in which the class resides

javac FirstProgram.java

– The result is a byte‐code program whose filename is the same as the y p g class name followed by .class

FirstProgram.class

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Running a Java Program Running a Java Program

A J b i th d

• A Java program can be given the run command ( java ) after all its classes have been compiled

– Only run the class that contains theOnly run the class that contains the mainmainmethod (themethod (the system will automatically load and run the other classes, if any)

The i method begins with the line – The mainmethod begins with the line:

public static void main(String[ ] args)

– Follow the run command by the name of the class only y y (no .javaor .classextension)

java FirstProgram

Syntax and Semantics Syntax and Semantics

• Syntax: The arrangement of words and

punctuations that are legal in a language, the

p g g g

grammar rules of a language

• Semantics: The meaning of things written

• Semantics: The meaning of things written while following the syntax rules of a language

Tip: Error Messages Tip: Error Messages

i k i

• Bug: A mistake in a program

– The process of eliminating bugs is called debugging

• Syntax error: A grammatical mistake in a y g program

– The compiler can detect these errors, and will The compiler can detect these errors, and will output an error message saying what it thinks the error is, and where it thinks the error is

Tip: Error Messages Tip: Error Messages

R ti A th t i t d t t d til

• Run‐time error: An error that is not detected until a program is run

– The compiler cannot detect these errors: an errorThe compiler cannot detect these errors: an error message is not generated after compilation, but after execution

L i A i t k i th d l i l ith

• Logic error: A mistake in the underlying algorithm for a program

– The compiler cannot detect these errors and no errorThe compiler cannot detect these errors, and no error message is generated after compilation or execution, but the program does not do what it is supposed to do

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Identifiers Identifiers

Id ifi Th f i bl h i

• Identifier: The name of a variable or other item (class, method, object, etc.) defined in a program

A J id tifi t t t t ith di it d ll th – A Java identifier must not start with a digit, and all the

characters must be letters, digits, or the underscore symboly

– Java identifiers can theoretically be of any length

– Java is a case‐sensitive language: Rate, rate, and RATE are the names of three different variables

Identifiers Identifiers

K d d R d d Id tifi th t h

• Keywords and Reserved words: Identifiers that have a predefined meaning in Java

– Do not use them to name anything elseDo not use them to name anything else

public class void static

• Predefined identifiers: Identifiers that are defined in libraries required by the Java language standard

– Although they can be redefined, this could be confusing and dangerous if doing so would change their standard and dangerous if doing so would change their standard meaning

System String println

Naming Conventions Naming Conventions

St t th f i bl l th d d

• Start the names of variables, classes, methods, and objects with a lowercase letter, indicate "word"

boundaries with an uppercase letter, and restrict the boundaries with an uppercase letter, and restrict the remaining characters to digits and lowercase letters

topSpeed bankRate1 timeOfArrival

• Start the names of classes with an uppercase letter and, otherwise, adhere to the rules above

Fi tP M Cl St i

FirstProgram MyClass String

Variable Declarations Variable Declarations

E i bl i J b d l d b f i i

• Every variable in a Java program must be declared before it is used

– A variable declaration tells the compiler what kind of data (type) willA variable declaration tells the compiler what kind of data (type) will be stored in the variable

– The type of the variable is followed by one or more variable names separated by commas, and terminated with a semicolon

separated by commas, and terminated with a semicolon

– Variables are typically declared just before they are used or at the start of a block (indicated by an opening brace {)

Basic types in Java are called primitive types – Basic types in Java are called primitive types

int numberOfBeans;

double oneWeight, totalWeight;

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Primitive Types Primitive Types

Assignment Statements With Primitive Types Assignment Statements With Primitive Types

• In Java, the assignment statement is used to change the value of a variable

The equal sign (=) is used as the assignment operator – The equal sign (=) is used as the assignment operator – An assignment statement consists of a variable on

the left side of the operator, and an expression on the right side of the operator

Variable = Expression;

– An expression consists of a variable, number, or mixAn expression consists of a variable, number, or mix of variables, numbers, operators, and/or method invocations

temperature = 98 6;

temperature = 98.6;

count = numberOfBeans;

Assignment Statements With Primitive Types Assignment Statements With Primitive Types

Wh i t t t t i t d th

– When an assignment statement is executed, the

expression is first evaluated, and then the variable on the left‐hand side of the equal sign is set equal to the value of

th i

the expression

distance = rate * time;

– Note that a variable can occur on both sides of theNote that a variable can occur on both sides of the assignment operator

count = count + 2;

– The assignment operator is automatically executed from right‐to‐left, so assignment statements can be chained

number2 = number1 = 3;

number2 number1 3;

Tip: Initialize Variables Tip: Initialize Variables

• A variable that has been declared but that has not yet been given a value by some means is said to be uninitialized

• In certain cases an uninitialized variable is given a default value

– It is best not to rely on this

– Explicitly initialized variables have the added benefit of improving program clarity

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Tip: Initialize Variables Tip: Initialize Variables

Th d l i f i bl b bi d i h

• The declaration of a variable can be combined with its initialization via an assignment statement

i t t 0

int count = 0;

double distance = 55 * .5;

char grade = 'A';

– Note that some variables can be initialized and others can remain uninitialized in the same declaration

int initialCount = 50, finalCount;

Shorthand Assignment Statements Shorthand Assignment Statements

Sh th d i t t ti bi th i t

• Shorthand assignment notation combines the assignment operator (=) and an arithmetic operator

• It is used to change the value of a variable by adding, g y g subtracting, multiplying, or dividing by a specified value

• The general form is

Variable Op = Expression Variable Op = Expression

which is equivalent to

Variable = Variable Op (Expression) – The Expressioncan be another variable, a constant, or a more

complicated expression

– Some examples of what Opcan be are +, -, *, /, or %

Shorthand Assignment Statements Shorthand Assignment Statements

Example: Equivalent To:

count += 2; count = count + 2;

sum -= discount; sum = sum – discount;

bonus *= 2; bonus = bonus * 2;

bonus = 2; bonus = bonus 2;

time /= time =

rushFactor; time / rushFactor;

change %= 100; change = change % 100;

amount *=

count1 + count2;

amount = amount * (count1 + count2);

;

Assignment Compatibility Assignment Compatibility

I l h l f b d i

• In general, the value of one type cannot be stored in a variable of another type

i t i tV i bl 2 99 //Ill l int intVariable = 2.99; //Illegal – The above example results in a type mismatch because a

doublevalue cannot be stored in anintvariable doublevalue cannot be stored in an intvariable

• However, there are exceptions to this

double doubleVariable = 2;

– For example, an intvalue can be stored in a double type

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Assignment Compatibility Assignment Compatibility

M ll l f t i th f ll i li t b

• More generally, a value of any type in the following list can be assigned to a variable of any type that appears to the right of itbyteshortintlongfloatdouble

char

– Note that as your move down the list from left to right, the range of allowed values for the types becomes larger

• An explicit type cast is required to assign a value of one type to a variable whose type appears to the left of it on the above yp pp list (e.g., doubleto int)

• Note that in Java an intcannot be assigned to a variable of typeboolean nor can abooleanbe assigned to a variable type boolean, nor can a booleanbe assigned to a variable of type int

Constants Constants

C t t ( lit l) A it i J hi h h

• Constant (or literal): An item in Java which has one specific value that cannot change

– Constants of an integer type may not be written with aConstants of an integer type may not be written with a decimal point (e.g., 10)

– Constants of a floating‐point type can be written in ordinary decimal fraction form (e g 367000 0or ordinary decimal fraction form (e.g., 367000.0or 0.000589)

– Constant of a floating‐point type can also be written in scientific (or floating‐point) notation (e.g., 3.67e5or 5.89e-4)

• Note that the number before the emay contain a decimal point, y p , but the number after the emay not

Constants Constants

C t t f t h d b l i

• Constants of type char are expressed by placing a single character in single quotes (e.g., 'Z')

• Constants for strings of characters are enclosed by

• Constants for strings of characters are enclosed by double quotes (e.g., "Welcome to Java")

• There are only two There are only two boolean boolean type constants, type constants, true true and false

– Note that they must be spelled with all lowercase letters

Arithmetic Operators and Expressions Arithmetic Operators and Expressions

i l i b

• As in most languages, expressions can be formed in Java using variables, constants, and arithmetic operators

– These operators are + (addition), - (subtraction),

* (multiplication), / (division), and % (modulo, remainder)

– An expression can be used anyplace it is legal to use a value of the type produced by the

i

expression

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Arithmetic Operators and Expressions Arithmetic Operators and Expressions

If ith ti t i bi d ithi t d

• If an arithmetic operator is combined with int operands, then the resulting type is int

• If an arithmetic operator is combined with one or two p doubleoperands, then the resulting type is double

• If different types are combined in an expression, then the resulting type is the right‐most type on the following list that resulting type is the right most type on the following list that is found within the expression

byteshortintlongfloatdouble char

char

– Exception: If the type produced should be byteor short(according to the rules above), then the type produced will actually be an int

Parentheses and Precedence Rules Parentheses and Precedence Rules

A i b f ll h i d i d

• An expression can be fully parenthesized in order to specify exactly what subexpressions are combined with each operator

with each operator

• If some or all of the parentheses in an expression are omitted Java will follow precedence rules to

omitted, Java will follow precedence rules to determine, in effect, where to place them

– However it's best (and sometimes necessary) to include – However, it s best (and sometimes necessary) to include

them

Precedence Rules Precedence Rules

Precedence and Associativity Rules Precedence and Associativity Rules

Wh th d f t dj t ti t b

• When the order of two adjacent operations must be determined, the operation of higher precedence (and its apparent arguments) is grouped before the (and its apparent arguments) is grouped before the operation of lower precedence

base + rate * hours is evaluated as base + (rate * hours)

• When two operations have equal precedence, the order of operations is determined by associativity order of operations is determined by associativity rules

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Precedence and Associativity Rules Precedence and Associativity Rules

– Unary operators of equal precedence are grouped right‐to‐

left

+ +rate is evaluated as+( (+rate)) +-+rate is evaluated as +(-(+rate))

– Binary operators of equal precedence are grouped left‐to‐

right right

base + rate + hours is evaluated as (base + rate) + hours

– Exception: A string of assignment operators is grouped right‐to‐left

n1 = n2 = n3; is evaluated as n1 = (n2 = n3);

Pitfall: Round‐Off Errors in Floating‐Point Numbers

• Floating point numbers are only approximate quantities

– Mathematically, the floating‐point number 1.0/3.0 is equal to 0.3333333 . . .

– A computer has a finite amount of storage space

• It may store 1.0/3.0 as something like 0.3333333333, which is slightly smaller than one‐third

slightly smaller than one‐third

– Computers actually store numbers in binary notation, but the consequences are the same: floating‐point numbers q g p may lose accuracy

Integer and Floating Point Division Integer and Floating‐Point Division

Wh b h d fl i i di i i

• When one or both operands are a floating‐point type, division results in a floating‐point type

15.0/25.0/ evaluates toe a uates to 7.5.5

• When both operands are integer types, division results in an integer type

– Any fractional part is discarded – The number is not rounded

15/2 evaluates to 7 15/2 evaluates to 7

• Be careful to make at least one of the operands a floating‐

point type if the fractional portion is needed

The % Operator The % Operator

• The % operator is used with operands of type int to recover the information lost after performing integer division

15/2 evaluates to the quotient 7 15%2 evaluates to the remainder 1

• The % operator can be used to count by 2's, 3's, or any other number

– To count by twos, perform the operation number % 2, and when the result is 0, numberis even

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Type Casting Type Casting

A k l f d d l f

• A type cast takes a value of one type and produces a value of another type with an "equivalent" value

– If nand ma d are integers to be divided, and the fractional portion of the a e tege s to be d ded, a d t e act o a po t o o t e result must be preserved, at least one of the two must be type cast to a floating‐point type before the division operation is performed

double ans = n / (double)m;

double ans n / (double)m;

– Note that the desired type is placed inside parentheses immediately in front of the variable to be cast

Note also that the type and value of the variable to be cast does not – Note also that the type and value of the variable to be cast does not

change

More Details About Type Casting More Details About Type Casting

Wh i f fl i i i

• When type casting from a floating‐point to an integer type, the number is truncated, not rounded

– (int)2.9( t) .9evaluates to 2, not 3e a uates to , ot3

• When the value of an integer type is assigned to a variable of a floating‐point type, Java performs an automatic type cast

ll d i

called a type coercion

double d = 5;

• In contrast it is illegal to place aIn contrast, it is illegal to place a doubledoublevalue into anvalue into an intint variable without an explicit type cast

int i = 5.5; // Illegal int i = (int)5.5 // Correct

Increment and Decrement Operators Increment and Decrement Operators

• The increment operator ( ++ ) adds one to the value of a variable

– If n is equal to 2 , then n++ or ++n will change the value of n to 3

value of n to 3

• The decrement operator ( -- ) subtracts one

f h l f i bl

from the value of a variable

– If n is equal to 4 , then n-- or --n will change the value of n to 3

Increment and Decrement Operators Increment and Decrement Operators

Wh ith t d it i bl d i

• When either operator precedes its variable, and is part of an expression, then the expression is evaluated using the changed value of the variable evaluated using the changed value of the variable

– If nis equal to 2, then 2*(++n)evaluates to 6

• When either operator follows its variable, and is part p p of an expression, then the expression is evaluated using the original value of the variable, and only then is the variable value changed

is the variable value changed

– If nis equal to 2, then 2*(n++)evaluates to 4

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The Class String The Class String

Th i i i i f i i J

• There is no primitive type for strings in Java

• The class Stringis a predefined class in Java that is used to store and process strings

store and process strings

• Objects of type Stringare made up of strings of characters that are written within double quotes

– Any quoted string is a constant of type String

"Live long and prosper."

• A variable of typeSt i can be given the value of a

• A variable of type Stringcan be given the value of a Stringobject

String blessing = "Live long and prosper.";g g g p p

Concatenation of Strings Concatenation of Strings

C i U i h i i d

• Concatenation: Using the +operator on two strings in order to connect them to form one longer string

– If greetingg eet gis equal to "Hello ", and javaClasss equa to e o , a dja aC assis equal to s equa to

"class", then greeting + javaClassis equal to "Hello class"

• Any number of strings can be concatenated together

• When a string is combined with almost any other type of item, the result is a stringg

– "The answer is " + 42 evaluates to

"The answer is 42"

Classes Objects and Methods Classes, Objects, and Methods

A l i h f h l bj

• A class is the name for a type whose values are objects

• Objects are entities that store data and take actions

– Objects of theStringclass store data consisting of strings of – Objects of the Stringclass store data consisting of strings of

characters

• The actions that an object can take are called methods

– Methods can return a value of a single type and/or perform an action – All objects within a class have the same methods, but each can have

different data values

Classes Objects and Methods Classes, Objects, and Methods

I ki lli h d h d i ll d i

• Invoking or calling a method: a method is called into action by writing the name of the calling object, followed by a dot followed by the method name followed by a dot, followed by the method name, followed by parentheses

– This is sometimes referred to as sending a message to the – This is sometimes referred to as sending a message to the

object

– The parentheses contain the information (if any) needed p ( y) by the method

– This information is called an argument (or arguments)

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String Methods String Methods

Th St i l t i f l th d f t i

• The Stringclass contains many useful methods for string‐

processing applications

– A Stringmethod is called by writing a Stringobject, a dot, the

f th th d d i f th t l

name of the method, and a pair of parentheses to enclose any arguments

– If a Stringmethod returns a value, then it can be placed anywhere that a value of its type can be used

that a value of its type can be used String greeting = "Hello";

int count = greeting.length();

S t t i tl ("L th i " + System.out.println("Length is " +

greeting.length());

– Always count from zero when referring to the position or index of a character in a string

character in a string

Some Methods in the Class String (Part 1 of 8) Some Methods in the Class String (Part 1 of 8)

Some Methods in the Class String (Part 2 of 8) Some Methods in the Class String (Part 2 of 8)

Some Methods in the Class String (Part 3 of 8) Some Methods in the Class String (Part 3 of 8)

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Some Methods in the Class String (Part 4 of 8) Some Methods in the Class String (Part 4 of 8)

Some Methods in the Class String (Part 5 of 8) Some Methods in the Class String (Part 5 of 8)

Some Methods in the Class String (Part 6 of 8)

Some Methods in the Class String (Part 6 of 8) Some Methods in the Class String (Part 7 of 8) Some Methods in the Class String (Part 7 of 8)

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Some Methods in the Class String (Part 8 of 8) Some Methods in the Class String (Part 8 of 8)

String Indexes String Indexes

Escape Sequences Escape Sequences

• A backslash ( \ ) immediately preceding a character (i.e., without any space) denotes an ( y p ) escape sequence or an escape character

– The character following the backslash does not – The character following the backslash does not

have its usual meaning

Alth h it i f d i t b l it i – Although it is formed using two symbols, it is

regarded as a single character

Escape Sequences Escape Sequences

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String Processing String Processing

ASt i bj t i J i id d t b i t bl i

• A Stringobject in Java is considered to be immutable, i.e., the characters it contains cannot be changed

• There is another class in Java calledThere is another class in Java called StringBufferStringBufferthat hasthat has methods for editing its string objects

• However, it is possible to change the value of a String variable by using an assignment statement

String name = "Soprano";

name = "Anthony " + name;

name = Anthony + name;

Character Sets Character Sets

ASCII A h d b i l

• ASCII: A character set used by many programming languages that contains all the characters normally used on an English‐

language keyboard, plus a few special charactersg g y , p p

– Each character is represented by a particular number

• Unicode: A character set used by the Java language that

i l d ll h ASCII h l f h h

includes all the ASCII characters plus many of the characters used in languages with a different alphabet from English

Naming Constants Naming Constants

I d f i " " b i l

• Instead of using "anonymous" numbers in a program, always declare them as named constants, and use their name instead

public static final int INCHES PER FOOT = 12;

p _ _ ;

public static final double RATE = 0.14;

– This prevents a value from being changed inadvertently

I h h dd d d h h l b difi d i

– It has the added advantage that when a value must be modified, it need only be changed in one place

– Note the naming convention for constants: Use all uppercase letters, and designate word boundaries with an underscore character

Comments Comments

A li t b i ith th b l // d

• A line comment begins with the symbols // , and causes the compiler to ignore the remainder of the line

line

– This type of comment is used for the code writer or for a programmer who modifies the code

bl k b h h b l /

• A block comment begins with the symbol pair /* , and ends with the symbol pair */

The compiler ignores anything in between – The compiler ignores anything in between – This type of comment can span several lines

– This type of comment provides documentation for the yp p users of the program

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Program Documentation Program Documentation

J ith ll d j d

• Java comes with a program called javadoc that will automatically extract documentation from block comments in the classes you define from block comments in the classes you define

– As long as their opening has an extra asterisk (/**)

• Ultimately, a well written program is self‐ y p g documenting

– Its structure is made clear by the choice of identifier names and the indenting pattern

names and the indenting pattern

– When one structure is nested inside another, the inside structure is indented one more level