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Java

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classHelloJava{ publicstaticvoidmain(String[]arguments){ System.out.println("Hello, Java"); } }

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classHelloJava{ publicstaticvoidmain(String[]arguments){ System.out.println("Hello, Java"); } } -

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classHelloJava{ publicstaticvoidmain(String[]arguments){ System.out.println("Hello, Java"); } } :

classHelloJava{publicstaticvoid main(String[]arguments){ System.out.println("Hello, Java");}}

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class HelloJava {public staticvoidmain( String[ ]arguments){ System. out.println("Hello, Java");}

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HelloJava.java

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abstract continue for new switch

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byte,

short, int, long, float, double, boolean, char, Object String),

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byte 0 -128 +127 short 0 -32768 +32767 int 0 -2147483648 +2147483647

long 0L -9223372036854775808

+9223372036854775807

float 0.0f -3.4+38 +3.4+38 double 0.0d -1.7+308 +1.7+308

boolean false true false char '\u0000' 0 +65535 Object null String null

byte, short, int, long, float, double, boolean char

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byte centuries = 20;

short years = 2000;

int days = 730480;

long hours = 17531520;

System.out.println(centuries + " centuries is " + years +

" years, or " + days + " days, or " + hours + " hours.");

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. byte, -

long

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20 centuries is 2000 years, or 730480 days, or 17531520 hours.

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float floatPI = 3.14f; double doublePI = 3.14;

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int a = 1; int b = 2; boolean greaterAB = (a > b); boolean equalA1 = (a == 1); if (greaterAB) { System.out.println("A > B"); } else { System.out.println("A

16

equalA1. greaterAB true,

>B, B>A

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char

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char, 'a', 'b' 'A'

char symbol = 'a';

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System.out.println( "The code of '" + symbol + "' is: " + (int) symbol); symbol = 'b'; System.out.println( "The code of '" + symbol + "' is: " + (int) symbol); symbol = 'A'; System.out.println( "The code of '" + symbol + "' is: " + (int) symbol); :

The code of 'a' is: 97 The code of 'b' is: 98 The code of 'A' is: 65

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String firstName = "Ivan"; String lastName = "Ivanov"; String fullName = firstName + " " + lastName; System.out.println("Hello, " + firstName + "!"); System.out.println("Your full name is " + fullName + "."); :

Hello, Ivan! Your full name is Ivan Ivanov.

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Object container = 5; Object container2 = "Five"; System.out.println("The value of container is: " + container); System.out.println("The value of container2 is: " + container2); :

The value of container is: 5 The value of container2 is: Five.

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byte centuries = 20; short years = 2000; int days = 730480; long hours = 17531520; float floatPI = 3.141592653589793238f; double doublePI = 3.141592653589793238; boolean isEmpty = true; char symbol = 'a'; String firstName = "Ivan";

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int firstValue = 5; int secondValue;

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int thirdValue; secondValue = firstValue; thirdValue = firstValue = 3;

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float

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isMale boolean

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int z = 4 + 8;

System.out.println(z); // 12

String firstName = "Lachezar";

String lastName = "Bozhkov";

String fullName = firstName + " " + lastName;

System.out.println(fullName);

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int squarePerimeter = 17;

double squareSide = squarePerimeter / 4.0;

double squareArea = squareSide * squareSide;

System.out.println(squareSide); // 4.25

System.out.println(squareArea); // 18.0625

int a = 5;

int b = 4;

System.out.println(a + b); // 9

System.out.println(a + b++); // 9


System.out.println(a + (++b)); // 11


System.out.println(14 / a); // 2

System.out.println(14 % a); // 4

(true

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true true false true true false true false false false true true false true true false true true false false true false false false , , ""

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boolean b = false;

System.out.println(a && b); // false

System.out.println(a || b); // true

System.out.println(!b); // true

System.out.println(b || true); // true

System.out.println((5>7) ^ (a==b)); // false

+ (String). ,

27

. String,

, String,

String

.

, :

String first = "Star";

String second = "Craft";

System.out.println(first + second); // StarCraft

String output = first + second + " ";

int number = 2;

System.out.println(output + number);

// StarCraft 2

String

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println(), .

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output.

output 2 ( number)

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short a = 3; // 0000 0011 = 3

short b = 5; // 0000 0101 = 5

System.out.println( a | b); // 0000 0111 = 7

System.out.println( a & b); // 0000 0001 = 1

System.out.println( a ^ b); // 0000 0110 = 6

29

System.out.println(~a & b); // 0000 0100 = 4

System.out.println(a 1); // 0000 0001 = 1

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publicclass RelationalOperatorsDemo {

publicstaticvoid main(String args[]) {

int x = 10, y = 5;

System.out.println("x > y : " + (x > y)); // true

System.out.println("x < y : " + (x < y)); // false

System.out.println("x >= y : " + (x >= y)); // true

System.out.println("x

31

1 = 2;

, :

int x = 6;

String helloString = " .";

int y = x;

6 x.

helloString,

x y.

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int a = 6;

int b = 4;

System.out.println(a > b ? "a>b" : "b

33

.

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(, ,

). :

int r = (150-20) / 2 + 5;

double surface = Math.PI * r * r;

double perimeter = 2 * Math.PI * r;

System.out.println(r);

System.out.println(surface);

System.out.println(perimeter);

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15393.804002589986

439.822971502571

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int a = 5;

int b = ++a;

System.out.println(a); // 6

System.out.println(b); // 6

34

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System.err

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print() println()

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(, ):

:

System.out.println("Hello, this is Java");

System.out.println(5);

System.out.println(3.14159265358979);

40

:

, System.out.println

,

println() PrintStream (

PrintStream

API- Java).

print() println(), print()

, ,

. println() "print line",

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print println

System.out.println("I love");

:

System.out.print("this ");

System.out.print("Book!");

:

I love

this Book!

, ,

. , println(),

"I love" .

41

print, ,

"this" "Book!

" .

printf()

printf()

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"C",

( BCPL).

printf()

Java. printf()

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Java

printf(, , , , )

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printf()

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:

String str = "Hello, Java!";

System.out.print(str);

System.out.printf("%s", str);

:

42

, "Hello, Java!

,

.

" . ,

.

printf().

printf() . %s ,

str, %s. printf() System.out, .

. PrintStream

:

.

String name = "Boris";

int age = 18;

String town = "Plovdiv";

System.out.printf(

"%s is %d years old from %s!\n", name, age, town);

:

printf() ,

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, (%s %d). %s

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name. %d, ,

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(town). \n,

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43

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InputStream. ()

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System.in.read()

Java Java ,, JVMJVM

System.in.readSystem.in.read()()

System.out.printlnSystem.out.println()()

STDIN

STDERR

STDOUT

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,

.

44

(STDIN) (STDOUT, STDERR) Java. STDERR

System.err.println("This is error!");

. :

.

.

PrintingLetter.java

publicclass PrintingLetter {

publicstaticvoid main(String[] args) {

Scanner input = new Scanner(System.in);

System.out.printf("Enter person name: ");

String person = input.nextLine();

System.out.printf("Enter book name: ");

String book = input.nextLine();

String from = "Authors Team";

System.out.printf(" Dear %s,%n", person);

System.out.printf("We are pleased to inform " +

45

"you that \"%2$s\" is the best Bulgarian book. \n" +

"The authors of the book wishes you good luck %s!%n",

person, book);

System.out.println(" Yours,");

System.out.printf(" %s", from);

}

}

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System.out.println("Enter two numbers.");

int firstNumber = input.nextInt();

int secondNumber = input.nextInt();

int biggerNumber = firstNumber;

if (secondNumber > firstNumber) {

biggerNumber = secondNumber;

}

System.out.printf("The bigger number is: %d%n", biggerNumber);

}

48

if

if

int a = 6;

-,

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if (a > 5)

System.out.println(" - 5.");

System.out.println(" !");

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49

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true, , else-

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x = 3;

if (x > 3) {

System.out.println("x - 3");

} else {

System.out.println("x - 3");

}

: x>3,

: "x - 3", (else) : "x -

3". , x=3,

else-. :

x - 3

if

if-, .

if if

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if if-else if else

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if . else if

.

50

,

.

,

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if

if


:

System.out.println(

"Please enter two numbers (on separate lines).");

int first = input.nextInt();

int second = input.nextInt();

if (first == second) {

System.out.println("These two numbers are equal.");

} else {

if (first > second) {

System.out.println("The first number is greater.");

} else {

System.out.println("The second number is greater.");

}

}

:

, ,

-. :

Please enter two numbers (on separate lines).

2

51

4

The second number is greater.

switch-case switch

.

switch-case ?

switch

( ).

:

switch ( ) {

case --1: ; break;

case --2: ; break;

case --3: ; break;

case --4: ; break;

default: ;}

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switch .

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switch.

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case ,

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switch

switch

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byte, char enum. , ,

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if

.

,

.

:

int number = 6;

53

switch (number) {

case 1:

case 4:

case 6:

case 8:

case 10: System.out.println(" !"); break;

case 2:

case 3:

case 5:

case 7: System.out.println(" !"); break;

default: System.out.println(" !");

}

case break ,

6,

case

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case ,

break.

:

1. if-,

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54

2. , (+ -)

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3. , - ,

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4. , -

5 .

5. . ,

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- {-2, -1, 1}, -1 1 0.

- {3, 1, -7}, 0.

6. ,

[1..9] :

- 1 3, 10.

- 4 6, 100.

- 7 9, 1000.

- 0 9, .

8. .

""?

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55

- ;

- .

, , (infinite).

while - while.

while (condition) {

statements;

}

Condition , true fasle.

loop condition.

Statements , .

.

while ,

true, ,

(pre-test loop). , while

:

true

Expression

Statement(s)

false

while

While .

56

while ,

0 9

:

int counter = 0;

while (counter < 10) {

System.out.printf("Number : %d%n", counter);

counter++;

}

:

,

.

1 N

while

1 N. N .

num sum 1. num ,

.

1, ,

,

57

1 N. Sum .

num.

num ( 1 N) "+"

.


System.out.print("n = ");

int n = input.nextInt();

int num = 1;

int sum = 1;

System.out.print("The sum 1");

while (num < n) {

num++;

sum += num;

System.out.printf("+%d", num);

}

System.out.printf(" = %d%n", sum);

:

break

break .

break,

,

, break .

58

while break.

.

n, ,

- n. n! :

- n! = 1*2*3.......(n-1)*n, n>1;

- 1! = 1;

- 0! = 1.

N! , - n:

- n! = (n-1)!n, 1! = 1.

, n.

factorial 1, n . While ,

, .

true. break, , n

1. n,

factorial, n 1.

: n*(n-1)*(n-2)**3*2, n=1

.



long factorial = 1;

while (true) {

if (n == 1) {

break;

}

factorial *= n;

59

n--;

}

System.out.println("n! = " + factorial);

10 , :

10

n! = 3628800

do-while Do-while while ,

.

(post-test loop).

do-while:

do {

statements;

}

while (expression);

do-while :

60

do-while

Do-while , ,

, - .

n,

while , do-while.

.

1, -

0. .


System.out.print("n = ");


long factorial = 1;

do {

factorial *= n;

n--;

} while (n > 0);

System.out.println("n! = " + factorial);

n=7:

n = 7

n! = 5040

for For- - while do-while,

- - .

for- :

61

for (initialization; test; update) {

statements;

}

, ,

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(infinite loop) for

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for ( ; ; ) {

statements;

}

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for (int num = 0; num < 10; ...) {

}

62

, . true

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for (int num = 0; num < 10; num++) {

}

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for-

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for (int small=1, large=10; small

63

continue

continue - ,

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sum = 141

for 5 Java

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statements;

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for (String town: towns) {

65

System.out.printf("%s ", town);

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78

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96

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100

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101

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System.out.println("Sun Microsystems");

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102

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103

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float max = number1;

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104

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printSign(-5);

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105

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publicstaticvoid printNumber(int numberParam) {

numberParam = 5;

System.out.println("in printNumber() method, after the "

+ "modification, numberParam is: " + numberParam);

}

main():


106

int numberArg = 3;

printNumber(numberArg);

System.out.println("in the main() method number is: " +

numberArg);

}

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System.out.println(Arrays.toString(arrParam));

}

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modifyArr():


int[] arrArg = newint[] { 1, 2, 3 };

System.out.print("Before modifyArr() the argument is: ");

System.out.println(Arrays.toString(arrArg));

modifyArr(arrArg);

108

System.out.print("After modifyArr() the argument is: ");

System.out.println(Arrays.toString(arrArg));

}

? :

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109

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publicstaticvoid printTotalAmountForBooks(double[] prices) {

double totalAmount = 0;

for (double singleBookPrice : prices) {

totalAmount += singleBookPrice;

}

System.out.println("The total amount of all books is: " +

totalAmount);

}

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double[] prices = newdouble[] { 3, 2.5 };

printTotalAmountForBooks(prices);

,

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printTotalAmountForBooks(3, 2.5);

printTotalAmountForBooks(3, 5.1, 10, 4.5);

110

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String companyLogo = getCompanyLogo();

111

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112

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113

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DataValidation.java

import java.util.Scanner;

publicclass DataValidation {



System.out.println("What time is it?");

System.out.print("Hours: ");

int hours = input.nextInt();

System.out.print("Minutes: ");

int minutes = input.nextInt();

boolean isValidTime =

validateHours(hours) &&validateMinutes(minutes);

if (isValidTime) {

System.out.printf(

"The time is %d:%d now.%n", hours, minutes);

} else {

System.out.println("Incorrect time!");

114

}

}

publicstaticboolean validateHours(int hours) {

boolean result = (hours >= 0) && (hours < 24);

return result;

}

publicstaticboolean validateMinutes(int minutes) {

boolean result = (minutes >= 0) && (minutes = 0) && (hours < 24);

return result;

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115

boolean result = (minutes >= 0) && (minutes

116

time is HH:mm now.", HH

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:

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Hours: 17

Minutes: 33

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:

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