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„Java – overview and basics”
„Java – overview and basics”
Literature
Literature
Programming language Platform Java language: Simple Architecture
Programming language Platform Java language: Simple Architecture
Brief history
Brief history
One compilation Many interpretations
One compilation Many interpretations
Java – compiled and interpreted
Java – compiled and interpreted
The Java platform has two components: The Java Virtual Machine (Java
The Java platform has two components: The Java Virtual Machine (Java
The essentials: Objects, strings, threads, numbers, input and output,
The essentials: Objects, strings, threads, numbers, input and output,
Security: Both low level and high level, including electronic
Security: Both low level and high level, including electronic
Standard Development Kit Java Runtime Enviroment
Standard Development Kit Java Runtime Enviroment
1) Copy j2sdk-1_6_0_<version number>-linux-i586
1) Copy j2sdk-1_6_0_<version number>-linux-i586
Question: What is the first thing you should check if the interpreter
Question: What is the first thing you should check if the interpreter
All tools are in pathtojdk/bin/ directory: javac - compiler, java -
All tools are in pathtojdk/bin/ directory: javac - compiler, java -
Create a Java source file
Create a Java source file
Creating first application
Creating first application
Write following code: import java
Write following code: import java
2. Write HTML file (HelloWorld
2. Write HTML file (HelloWorld
Comments in Java Code
Comments in Java Code
Class (template) Instanciation – creation of an Object Variables
Class (template) Instanciation – creation of an Object Variables
public static void main(String[] args) To launch an application is
public static void main(String[] args) To launch an application is
System
System
1) import java
1) import java
Packages are used to group classes, similar to the way libraries are
Packages are used to group classes, similar to the way libraries are
Can't Locate the Compiler javac: Command not found Solution: Modify
Can't Locate the Compiler javac: Command not found Solution: Modify
Can't Find Class Can't find class HelloWorldApp
Can't Find Class Can't find class HelloWorldApp
Java language
Java language
An object is a software bundle of variables and related methods
An object is a software bundle of variables and related methods
Encapsulation benefits: Modularity: The source code for an object can
Encapsulation benefits: Modularity: The source code for an object can
Message Software objects interact and communicate with each other by
Message Software objects interact and communicate with each other by
The three components of a message: 1) The object to which the message
The three components of a message: 1) The object to which the message
A class is a prototype that defines the variables and the methods
A class is a prototype that defines the variables and the methods
Inheritance Superclass Subclass
Inheritance Superclass Subclass
Inheritance benefits: Subclasses provide specialized behaviors from
Inheritance benefits: Subclasses provide specialized behaviors from
An interface is a device that unrelated objects use to interact with
An interface is a device that unrelated objects use to interact with
Interfaces benefits: Capturing similarities among unrelated classes
Interfaces benefits: Capturing similarities among unrelated classes
An object stores its state in variables
An object stores its state in variables
Variables (2)
Variables (2)
Primitive data types: Keyword Size/Format byte 8-bit short 16-bit int
Primitive data types: Keyword Size/Format byte 8-bit short 16-bit int
Variable name: 1) It must be a legal identifier
Variable name: 1) It must be a legal identifier
By Convention : Variable names begin with a lowercase letter
By Convention : Variable names begin with a lowercase letter
Variables (6)
Variables (6)
The value of a final variable cannot change after it has been
The value of a final variable cannot change after it has been
Variables (8)
Variables (8)
An operator performs a function on one, two, or three operands
An operator performs a function on one, two, or three operands
Arithmetic operators:
Arithmetic operators:
Arithmetic operators - conversions:
Arithmetic operators - conversions:
Arithmetic operators :
Arithmetic operators :
public class SortDemo { public static void main(String[] args) { int[]
public class SortDemo { public static void main(String[] args) { int[]
Relational operators :
Relational operators :
Conditional operators :
Conditional operators :
Question: 13 >> 1 =
Question: 13 >> 1 =
Operator
Operator
public class BitwiseDemo { static final int VISIBLE = 1; static final
public class BitwiseDemo { static final int VISIBLE = 1; static final
Operator
Operator
Other operators:
Other operators:
Operators (13)
Operators (13)
Operators (14)
Operators (14)
Statement type
Statement type
while (expression) { statement(s) } do { statement(s) } while
while (expression) { statement(s) } do { statement(s) } while
if (expression) { statement(s) } if (expression) { // code to perform
if (expression) { statement(s) } if (expression) { // code to perform
try { statement(s) } catch (exceptiontype name) { statement(s) }
try { statement(s) } catch (exceptiontype name) { statement(s) }
Break, continue and return
Break, continue and return
Control Flow Statements(2)
Control Flow Statements(2)
Control Flow Statements(3)
Control Flow Statements(3)

Презентация: «„Java – overview and basics”». Автор: konrad szumigaj. Файл: «„Java – overview and basics”.ppt». Размер zip-архива: 712 КБ.

„Java – overview and basics”

содержание презентации «„Java – overview and basics”.ppt»
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1 „Java – overview and basics”

„Java – overview and basics”

2 Literature

Literature

English-language sites: http://java.sun.com http://www.javaworld.com, http://www.javareport.com, http://www.jars.com, http://www.gamelon.com, http://www.javalobby.com http:// ... Polish-language sites: http://www.java.pl http://www.javasoft.pl http://www.webdeveloper.pl

Books: „Thinking in Java” Bruce Eckel English edition: http://www.bruceeckel.com (older free, newest payable) Polish Edition: http://www.helion.pl (payable) ...

Java – Overview and Basics

3 Programming language Platform Java language: Simple Architecture

Programming language Platform Java language: Simple Architecture

neutral Object oriented Portable Secure

Distributed High performance Interpreted Multithreaded

What is Java?

Java – Overview and Basics

4 Brief history

Brief history

1990 – suggestion in report „Further” concerning creation of new object oriented environment 1991 – OAK („Object Application Kernel”) language (James Gosling) 1995 – new language name: „Java” 1996 - Netscape compatible with Java 1.0. Sun propagates Java 1.0 environment 2001 – Java 1.4.0 – over 2100 classes library 2004 – Java 1.5.0 2007 – Java 1.6.0

Java – Overview and Basics

5 One compilation Many interpretations

One compilation Many interpretations

Java – compiled and interpreted

Java – Overview and Basics

6 Java – compiled and interpreted

Java – compiled and interpreted

Java – Overview and Basics

7 The Java platform has two components: The Java Virtual Machine (Java

The Java platform has two components: The Java Virtual Machine (Java

VM) The Java Application Programming Interface (Java API)

Java platform

Java – Overview and Basics

8 The essentials: Objects, strings, threads, numbers, input and output,

The essentials: Objects, strings, threads, numbers, input and output,

data structures, system properties, date and time, and so on. Applets: The set of conventions used by applets. Networking: URLs, TCP (Transmission Control Protocol), UDP (User Datagram Protocol) sockets, and IP (Internet Protocol) addresses. Internationalization: Help for writing programs that can be localized for users worldwide. Programs can automatically adapt to specific locales and be displayed in the appropriate language.

Java features

Java – Overview and Basics

9 Security: Both low level and high level, including electronic

Security: Both low level and high level, including electronic

signatures, public and private key management, access control, and certificates. Software components: Known as JavaBeansTM, can plug into existing component architectures. Object serialization: Allows lightweight persistence and communication via Remote Method Invocation (RMI). Java Database Connectivity (JDBCTM): Provides uniform access to a wide range of relational databases.

Java features (2)

Java – Overview and Basics

10 Standard Development Kit Java Runtime Enviroment

Standard Development Kit Java Runtime Enviroment

SDK & JRE

Java – Overview and Basics

11 1) Copy j2sdk-1_6_0_<version number>-linux-i586

1) Copy j2sdk-1_6_0_<version number>-linux-i586

bin to the directory into which you want to install the Java 2 SDK. (example:) /usr/local/ 2) Run j2sdk-1_6_0_<version number>-linux-i586.bin chmod a+x j2sdk-1_6_0_<version number>-linux-i586.bin ./j2sdk-1_6_0_<version number>-linux-i586.bin 3) Set enviromental variables to point jdk installation: export PATH=$PATH:/pathtojdk/bin export CLASSPATH=$CLASSPATH:/pathtojdk/lib:. (example:) export PATH=$PATH:/usr/local/j2sdk-1_4_0_01/bin

Linux installation instructions

Java – Overview and Basics

12 Question: What is the first thing you should check if the interpreter

Question: What is the first thing you should check if the interpreter

returns the error: Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorldApp.java.

Answer: Check your CLASSPATH. Probably current working directory is not included.

Linux installation instructions(2)

Java – Overview and Basics

13 All tools are in pathtojdk/bin/ directory: javac - compiler, java -

All tools are in pathtojdk/bin/ directory: javac - compiler, java -

interpreter, javadoc – generator of API documentation, appletviewer – applet browser, jar – tool for jar files jdb - debuggger,

Important tools

Java – Overview and Basics

14 Create a Java source file

Create a Java source file

A source file contains text, written in the Java programming language, that you and other programmers can understand. Compile the source file into a bytecode file. The Java compiler, javac, takes your source file and translates its text into instructions that the Java Virtual Machine (Java VM) can understand. The compiler puts these instructions into a bytecode file. Run the program contained in the bytecode file. The Java VM is implemented by a Java interpreter, java. This interpreter takes your bytecode file and carries out the instructions by translating them into instructions that your computer can understand.

Creating first application

Java – Overview and Basics

15 Creating first application

Creating first application

1. Write following code: class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); // Display "Hello World!" } } 2. Compile it: javac HelloWorldApp.java 3. Run the program: java HelloWorldApp

Java – Overview and Basics

16 Write following code: import java

Write following code: import java

applet.*; import java.awt.*; public class HelloWorld extends Applet { public void paint(Graphics g) { g.drawString("Hello world!", 50, 25); // Display "Hello world!" } }

Creating first applet

Java – Overview and Basics

17 2. Write HTML file (HelloWorld

2. Write HTML file (HelloWorld

html): <HTML> <HEAD> <TITLE>The Hello World Applet</TITLE> </HEAD> <BODY> <APPLET CODE="HelloWorld.class" WIDTH=150 HEIGHT=25> </APPLET> </BODY> </HTML>

3. Compile the source file: javac HelloWorld.java 4. Run the program: appletviewer HelloWorld.html

Creating first applet (2)

Java – Overview and Basics

18 Comments in Java Code

Comments in Java Code

The Java language supports three kinds of comments: /* text */ The compiler ignores everything from /* to */. /** documentation */ This indicates a documentation comment The compiler ignores this kind of comment, just like it ignores comments that use /* and */. The JDK javadoc tool uses doc comments when preparing automatically generated documentation. // text The compiler ignores everything from // to the end of the line.

Java – Overview and Basics

19 Class (template) Instanciation – creation of an Object Variables

Class (template) Instanciation – creation of an Object Variables

Methods

Defining a class

Java – Overview and Basics

20 public static void main(String[] args) To launch an application is

public static void main(String[] args) To launch an application is

necessary to implement this method. If no, the similar error message is displayed by compiler: In class NoMain: void main(String argv[]) is not defined 2. The main method accepts a single argument: an array of elements of type String.

The main method

Java – Overview and Basics

21 System

System

out.println(„HelloWorld”); – class .out – full name of variable out. When the class is loaded into the application, it instantiates PrintStream and assigns the new PrintStream object to the out class variable PrintStream – type of object out. It has method: println(String);

Using an instance method or variable

Java – Overview and Basics

22 1) import java

1) import java

applet.Applet; import java.awt.Graphics; public class HelloWorld extends Applet { public void paint(Graphics g) { g.drawString("Hello world!", 50, 25); } } public class HelloWorld extends java.applet.Applet { public void paint(java.awt.Graphics g) { g.drawString("Hello world!", 50, 25); } }

Importing classes and packages

Java – Overview and Basics

23 Packages are used to group classes, similar to the way libraries are

Packages are used to group classes, similar to the way libraries are

used to group C functions. Every class is in package If the source code for a class doesn't have a package statement at the top, declaring the package the class is in, then the class is in the default package. Within a package, all classes can refer to each other without prefixes. For example, the java.awt Component class refers to the java.awt Graphics class without any prefixes, without importing the Graphics class.

Importing classes and packages (2)

Java – Overview and Basics

24 Can't Locate the Compiler javac: Command not found Solution: Modify

Can't Locate the Compiler javac: Command not found Solution: Modify

your PATH environment variable so that it includes the directory where the Java compiler lives.

Common Compiler problem

Java – Overview and Basics

25 Can't Find Class Can't find class HelloWorldApp

Can't Find Class Can't find class HelloWorldApp

class Solution: The argument to the Java interpreter is the name of the class that you want to use, not the filename (HelloWorldApp instead of HelloWorldApp.class)

Common Interpreter problem

Java – Overview and Basics

26 Java language

Java language

Java – Overview and Basics

27 An object is a software bundle of variables and related methods

An object is a software bundle of variables and related methods

Visual representation of a software object:

Bicycle modeled as a software object:

Object Oriented Programming (OOP) concepts

Java – Overview and Basics

28 Encapsulation benefits: Modularity: The source code for an object can

Encapsulation benefits: Modularity: The source code for an object can

be written and maintained independently of the source code for other objects. Also, an object can be easily passed around in the system. Information hiding: An object has a public interface that other objects can use to communicate with it. The object can maintain private information and methods that can be changed at any time without affecting the other objects that depend on it.

OOP concepts (2)

Java – Overview and Basics

29 Message Software objects interact and communicate with each other by

Message Software objects interact and communicate with each other by

sending messages to each other. When object A wants object B to perform one of B's methods, object A sends a message to object B

OOP concepts (3)

Java – Overview and Basics

30 The three components of a message: 1) The object to which the message

The three components of a message: 1) The object to which the message

is addressed (YourBicycle) 2) The name of the method to perform (changeGears) 3) Any parameters needed by the method (lowerGear)

OOP concepts (4)

Java – Overview and Basics

31 A class is a prototype that defines the variables and the methods

A class is a prototype that defines the variables and the methods

common to all objects of a certain kind.

Visual representation of class:

Visual representation of bike class:

OOP concepts (5)

Java – Overview and Basics

32 Inheritance Superclass Subclass

Inheritance Superclass Subclass

OOP concepts (6)

Java – Overview and Basics

33 Inheritance benefits: Subclasses provide specialized behaviors from

Inheritance benefits: Subclasses provide specialized behaviors from

the basis of common elements provided by the superclass. Through the use of inheritance, programmers can reuse the code in the superclass many times. Programmers can implement superclasses called abstract classes that define "generic" behaviors. The abstract superclass defines and may partially implement the behavior, but much of the class is undefined and unimplemented. Other programmers fill in the details with specialized subclasses.

OOP concepts (7)

Java – Overview and Basics

34 An interface is a device that unrelated objects use to interact with

An interface is a device that unrelated objects use to interact with

each other. It is most analogous to a protocol (an agreed on behavior). Example: Inventory Interface To work in the inventory program, the bicycle class must agree to this protocol by implementing the interface. When a class implements an interface, the class agrees to implement all the methods defined in the interface.

OOP concepts (8)

Java – Overview and Basics

35 Interfaces benefits: Capturing similarities among unrelated classes

Interfaces benefits: Capturing similarities among unrelated classes

without forcing a class relationship. Declaring methods that one or more classes are expected to implement. Revealing an object's programming interface without revealing its class.

OOP concepts (9)

Java – Overview and Basics

36 An object stores its state in variables

An object stores its state in variables

A variable is an item of data named by an identifier. The variable's type determines what values it can hold and what operations can be performed on it. To give a variable a type and a name, you write a variable declaration, which generally looks like this: type name A variable has scope.

Variables

Java – Overview and Basics

37 Variables (2)

Variables (2)

Every variable must have a data type Java has two categories of data types: primitive and reference A variable of primitive type contains a single value of the appropriate size and format for its type: a number, a character, or a boolean value Arrays, classes, and interfaces are reference types. The value of a reference type variable, in contrast to that of a primitive type, is a reference to (an address of) the value or set of values represented by the variable. A reference is called a pointer, or a memory address. The Java does not support the explicit use of addresses like other languages do. You use the variable's name instead.

Java – Overview and Basics

38 Primitive data types: Keyword Size/Format byte 8-bit short 16-bit int

Primitive data types: Keyword Size/Format byte 8-bit short 16-bit int

32-bit long 64-bit float 32-bit double 64-bit char 16-bit boolean true or false

The format and size of primitive data types is independent from the platform on which a program is running !

Variables (3)

Java – Overview and Basics

39 Variable name: 1) It must be a legal identifier

Variable name: 1) It must be a legal identifier

An identifier is an unlimited series of Unicode characters that begins with a letter. 2 ) It must not be a keyword, a boolean literal (true or false), or the reserved word null. 3) It must be unique within its scope.

Variables (4)

Java – Overview and Basics

40 By Convention : Variable names begin with a lowercase letter

By Convention : Variable names begin with a lowercase letter

Class names begin with an uppercase letter. If a variable name consists of more than one word, the words are joined together, and each word after the first begins with an uppercase letter, like this: isVisible. The underscore character (_) is acceptable anywhere in a name, but by convention is used only to separate words in constants (because constants are all caps by convention and thus cannot be case-delimited).

Variables (5)

Java – Overview and Basics

41 Variables (6)

Variables (6)

A variable's scope is the region of a program within which the variable can be referred to by its simple name. The location of the variable declaration within your program establishes its scope and places it into one of these four categories:

Java – Overview and Basics

42 The value of a final variable cannot change after it has been

The value of a final variable cannot change after it has been

initialized. Such variables are similar to constants in other programming languages. To declare a final variable, use the final keyword in the variable declaration before the type: final int aFinalVar = 0; It is possible declare the local variable and initialize it later (but only once): final int blankfinal; . . . blankfinal = 0;

Variables (7)

Java – Overview and Basics

43 Variables (8)

Variables (8)

Question: Which of the following are valid variable names? int anInt i i1 1 thing1 1thing ONE-HUNDRED ONE_HUNDRED

Question: Which of the following are valid variable names? Answer: int anInt i i1 1 thing1 1thing ONE-HUNDRED ONE_HUNDRED

Java – Overview and Basics

44 An operator performs a function on one, two, or three operands

An operator performs a function on one, two, or three operands

Unary operators (example: ++) (postfix and prefix) Binary operators (example: +) (infix) Ternary operators ( example: ?:) (infix)

Operators

Java – Overview and Basics

45 Arithmetic operators:

Arithmetic operators:

Operators (2)

Operator

Use

Description

+

op1 + op2

Adds op1 and op2

-

op1 – op2

Subtracts op2 from op1

*

op1 * op2

Multiplies op1 by op2

/

op1 / op2

Divides op1 by op2

%

op1 % op2

Computes the remainder of dividing op1 by op2

Java – Overview and Basics

46 Arithmetic operators - conversions:

Arithmetic operators - conversions:

Operators (3)

Data Type of Result

Data Type of Operands

long

Neither operand is a float or a double (integer arithmetic); at least one operand is a long.

int

Neither operand is a float or a double (integer arithmetic); neither operand is a long.

double

At least one operand is a double.

float

At least one operand is a float; neither operand is a double.

Java – Overview and Basics

47 Arithmetic operators :

Arithmetic operators :

Operators (4)

Operator

Use

Description

+

+ op

Promotes op to int if it's a byte, short, or char

-

– op

Arithmetically negates op

++

op ++

Increments op by 1; evaluates to the value of op before it was incremented

++

++ op

Increments ... (after)

--

op --

Decrements ... (before)

--

-- op

Decrements ... (after)

Java – Overview and Basics

48 public class SortDemo { public static void main(String[] args) { int[]

public class SortDemo { public static void main(String[] args) { int[]

arrayOfInts = { 32, 87, 3, 589, 12, 8, 622, 127 }; for (int i = arrayOfInts.length; --i >= 0; ) { for (int j = 0; j < i; j++) { if (arrayOfInts[j] > arrayOfInts[j+1]) { int temp = arrayOfInts[j]; arrayOfInts[j] = arrayOfInts[j+1]; arrayOfInts[j+1] = temp; } } } } }

Operators (5)

Java – Overview and Basics

49 Relational operators :

Relational operators :

Operators (6)

Operator

Use

Returns true if

>

op1 > op2

op1 is greater than op2

>=

op1 >= op2

op1 is greater than or equal to op2

<

op1 < op2

op1 is less than op2

<=

op1 <= op2

op1 is less than or equal to op2

==

op1 == op2

op1 and op2 are equal

!=

op1 != op2

op1 and op2 are not equal

Java – Overview and Basics

50 Conditional operators :

Conditional operators :

Operators (7)

Operator

Use

Returns true if

&&

op1 && op2

op1 and op2 are both true, conditionally evaluates op2

||

op1 || op2

either op1 or op2 is true, conditionally evaluates op2

!

! op

op is false

&

op1 & op2

op1 and op2 are both true, always evaluates op1 and op2

|

op1 | op2

either op1 or op2 is true, always evaluates op1 and op2

^

op1 ^ op2

if op1 and op2 are different

Java – Overview and Basics

51 Question: 13 >> 1 =

Question: 13 >> 1 =

Answer: 6 13(1101) >> 1 = 6 (0110)

Shift operators :

Operators (8)

Operator

Use

Description

>>

op1 >> op2

shift bits of op1 right by distance op2

<<

op1 << op2

shift bits of op1 left by distance op2

>>>

op1 >>> op2

shift bits of op1 right by distance op2 (unsigned)

Java – Overview and Basics

52 Operator

Operator

Use

Operation

&

op1 & op2

|

op1 | op2

^

op1 ^ op2

~

~ op

Logical operators :

bitwise and

bitwise or

bitwise xor

bitwise complement

Operators (9)

Java – Overview and Basics

53 public class BitwiseDemo { static final int VISIBLE = 1; static final

public class BitwiseDemo { static final int VISIBLE = 1; static final

int DRAGGABLE = 2; static final int SELECTABLE = 4; static final int EDITABLE = 8; public static void main(String[] args) { int flags = 0; flags = flags | VISIBLE; flags = flags | DRAGGABLE; if ((flags & VISIBLE) == VISIBLE) { if ((flags & DRAGGABLE) == DRAGGABLE) { System.out.println("Flags are Vis. and Drag."); } } } }

Operators (10)

Java – Overview and Basics

54 Operator

Operator

Use

Equivalent to

+= (arithmetic)

op1 += op2

&= (logical)

op1 &= op2

>>= (shift)

op1 >>= op2

Assignments operators (examples):

op1 = op1 + op2

op1 = op1 & op2

op1 = op1 >> op2

Operators (11)

Java – Overview and Basics

55 Other operators:

Other operators:

Operators (12)

Operator

Description

?:

Shortcut if-else statement example : a == 1 ? true : false;

[]

Used to declare arrays, create arrays, and access array elements

.

Used to form qualified names

{ params }

Delimits a comma-separated list of parameters

( type )

Casts (converts) a value to the specified type

Java – Overview and Basics

56 Operators (13)

Operators (13)

Other operators: The new operator creates a new object or a new array. Example: creating a new Integer object from the Integer class in the java.lang package: Integer anInteger = new Integer(10); The instanceof operator tests whether its first operand is an instance of its second. op1 instanceof op2 op1 must be the name of an object and op2 must be the name of a class. An object is considered to be an instance of a class if that object directly or indirectly descends from that class.

Java – Overview and Basics

57 Operators (14)

Operators (14)

Operators precedence: [] . (params) expr++ expr-- ++expr --expr +expr -expr ~ ! new (type)expr * / % + - << >> >>> < > <= >= == != &

^ | && || ? : = += -= *= /= %= &= ^= |= <<= >>= >>>=

Java – Overview and Basics

58 Statement type

Statement type

Keyword

looping

while, do-while , for

decision making

if-else, switch-case

exception handling

try-catch-finally, throw

branching

break, continue, label:, return

Control Flow Statements

Java – Overview and Basics

59 while (expression) { statement(s) } do { statement(s) } while

while (expression) { statement(s) } do { statement(s) } while

(expression);

for (initialization; termination; increment) { statement } for ( ; ; ) { // infinite loop ... }

While, do-while and for

Java – Overview and Basics

60 if (expression) { statement(s) } if (expression) { // code to perform

if (expression) { statement(s) } if (expression) { // code to perform

true } else { // code to perform false }

switch (intVariable) { case 1: System.out.println(„1"); break; default: System.out.println(„The number is wrong !"); break; }

If, if-else and switch

Java – Overview and Basics

61 try { statement(s) } catch (exceptiontype name) { statement(s) }

try { statement(s) } catch (exceptiontype name) { statement(s) }

finally { statement(s) }

Try, catch and finally

Java – Overview and Basics

62 Break, continue and return

Break, continue and return

Break and continue: 1) break; || continue; 2) break label; || continue label; Example (by analogy is continue): ... search: for ( ; i < arrayOfInts.length; i++) { for (j = 0; j < arrayOfInts[i].length; j++) { if (arrayOfInts[i][j] == searchfor) { foundIt = true; break search; } } }

Return: 1) return value; 2) return;

Java – Overview and Basics

63 Control Flow Statements(2)

Control Flow Statements(2)

Question: What's wrong with the following code : if (i = 1) { /* do something */ }

Answer: Condition is ALWAYS true. Typical mistake of programmers: = is an assignment == is a comparison Ussually compiler warns about it.

Java – Overview and Basics

64 Control Flow Statements(3)

Control Flow Statements(3)

Question: What is an output if aNumber = 2? if (aNumber >= 0) if (aNumber == 0) System.out.println("first string"); else System.out.println("second string"); System.out.println("third string");

Answer: second string third string

Java – Overview and Basics

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