2. Java Basics. Java Statements

Август 10, 2022

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2. Java Basics. Java Statements

Содержание

2. Comments /* . . . */ - multi line comment // . . . - single-line
3. How to Use Comments Comments should be used to give overviews of code and provide additional
4. Variables Variables declaration: int k; double x = 2.1; Local variable should be initialized before it
5. 1. What will this program output? public class InitTest { public static void main (String[] args)
6. 2. What will this program output? public class Oblzm { public static void main (String args[]){
7. 3. What will this program output? public class Oblzm { public static void main (String args[]){
8. 4. What will this program output? public class Oblzm { public static void main (String args[]){
9. Constant Declaration final modifier: final int a = 42; // a = 12; - compile error
10. If-Then_Else Statement I if (boolean_expression) { statements } if (boolean_expression) { statements } else { statements
11. If-Then_Else Statement II if (boolean_expression) { statements; } else if (boolean_expression) { statements; } else if
12. If-Then-Else Example int a = 10; if (a > 0) { System.out.println("Positive"); } else if (a
13. Switch Statement switch(integral-expression) { case integer-value1 : statements; case integer-value2 : statements; break; case integer-value3 :
14. Switch Example char c = ’b’; switch(c) { case ’a’: case ’e’: case ’i’: case ’o’:
15. Switch Statement Expressions You can use enumerations as switch expression and case values You can use
16. While and Do-While Statement while (boolean_expression) { statements; } do { statements; } while (boolean_expression); *
17. While Example double a = 100.; while (a >= 1) { System.out.println(a); a /= 2.; }
18. Do-While Example double a = 0.5; do { System.out.println(a); a /= 2.; } while (a >=
19. For Statement for (initialization; Boolean-expression; step) { statements; } * Infopulse Training Center
20. For Examples for (int i = 10, k = 20; i System.out.println(i + " " +
21. Break and Continue Statements break quits the loop without executing the rest of the statements in
22. Use Break with a Label L: for … { for…{ break L; } } * Infopulse
23. Exercise 2.2.1. Find and print all divisors of a given natural number n. * Infopulse Training
24. Exercise 2.2.1. See 221Divisors project for the full text. * Infopulse Training Center
25. Exercise 2.2.2. Find and print all prime divisors of a given natural number n. * Infopulse
26. Exercise 2.2.3. Find sum of an infinite row for a given x Compare result with a
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Слайд 2

Comments
/* . . . */ - multi line comment
// .

. . - single-line comment
/** . . . */ - comment for documentation. It can include some additional tags (e.g. @version, @author, @param, @return).

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Слайд 3

How to Use Comments
Comments should be used to give overviews of

code and provide additional information that is not readily available in the code itself
Comments should contain only information that is relevant to reading and understanding the program
Doc comments describe Java classes, interfaces, constructors, methods, and ﬁelds
Java associates documentation comments with the ﬁrst declaration after the comment

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Слайд 4

Variables
Variables declaration: int k;
double x = 2.1;
Local variable should be

initialized before it will be used.
Variable scope is a block where it was declared.
Sub block can’t contain duplicated variable declaration.

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1. What will this program output?
public class InitTest {
public static

void main (String[] args) {
int a = 5;
int b;
if (a < 0) b = 10;
if (a >= 0) b = 50 ;
System.out.println(b);
}
}

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Слайд 6

2. What will this program output?
public class Oblzm {
public static

void main (String args[]){
int i = 5;
{
int j = 2;
System.out.println("Result is " + i * j);
}
}
}

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Слайд 7

3. What will this program output?
public class Oblzm {
public static

void main (String args[]){
int i = 5;
{
int j = 2;
}
System.out.println("Result is “ + i * j);
}
}

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Слайд 8

4. What will this program output?
public class Oblzm {
public static

void main (String args[]){
int i = 5;
{
int j = 2;
int i = 4;
System.out.println("Result is " + i * j);
}
}
}

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Слайд 9

Constant Declaration
final modifier: final int a = 42;
// a =

12; - compile error

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Слайд 10

$If-Then_Else Statement I if (boolean_expression) { statements } if (boolean_expression) {$

If-Then_Else Statement I
if (boolean_expression) {
statements
}
if (boolean_expression) {
statements
} else {
statements
}
*
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Center

Слайд 11

$If-Then_Else Statement II if (boolean_expression) { statements; } else if (boolean_expression)$

If-Then_Else Statement II
if (boolean_expression) {
statements;
} else if (boolean_expression) {
statements;
} else if

(boolean_expression) {
statements;
}

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Слайд 12

If-Then-Else Example
int a = 10;
if (a > 0) {
System.out.println("Positive");
}
else if (a

< 0) {
System.out.println("Negative");
}
else {
System.out.println("Zero");
}

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Слайд 13

Switch Statement
switch(integral-expression) {
case integer-value1 :
statements;
case integer-value2 :

statements;
break;
case integer-value3 :
statements;
break;
default:
statements;
}

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Слайд 14

Switch Example
char c = ’b’;
switch(c) {
case ’a’:
case ’e’:
case

’i’:
case ’o’:
case ’u’:
print("vowel");
break;

case ‘y’:
case ‘w’:
print("Sometimes a vowel");
break;
default:
print("consonant");
}

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Слайд 15

Switch Statement Expressions
You can use enumerations as switch expression and case

values
You can use strings as switch expression and case values (since Java 7 only!)

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Слайд 16

$While and Do-While Statement while (boolean_expression) { statements; } do {$

While and Do-While Statement
while (boolean_expression) {
statements;
}
do {
statements;
} while (boolean_expression);
*
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Training Center

Слайд 17

While Example
double a = 100.;
while (a >= 1) {
System.out.println(a);

a /= 2.;
}

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Слайд 18

Do-While Example
double a = 0.5;
do {
System.out.println(a);
a /= 2.;

} while (a >= 1);

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Слайд 19

For Statement
for (initialization; Boolean-expression; step) {
statements;
}
*
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Слайд 20

For Examples
for (int i = 10, k = 20; i <

k; i++, k--) {
System.out.println(i + " " + k);
}
for (char i = 's'; i >= 'b'; i--) System.out.println(i);

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Слайд 21

Break and Continue Statements
break quits the loop without executing the rest

of the statements in the loop.
continue stops the execution of the current iteration and goes back to the beginning of the loop to begin the next iteration.
You can use a label before an iteration statement and in break / continue statements interrupt the loops up to where the label exists

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Слайд 22

Use Break with a Label
L: for … {
for…{
break L;

}
}

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Слайд 23

Exercise 2.2.1.
Find and print all divisors of a given natural number

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Слайд 24

Exercise 2.2.1.
See 221Divisors project for the full text.
*
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Слайд 25

Exercise 2.2.2.
Find and print all prime divisors of a given natural

number n.

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Слайд 26

Exercise 2.2.3.
Find sum of an infinite row for a given x
Compare

result with a Math.exp(x) method value

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2. Java Basics. Java Statements

Содержание

Comments/* . . . */ - multi line comment // .

How to Use CommentsComments should be used to give overviews of

VariablesVariables declaration: int k; double x = 2.1;Local variable should be

1. What will this program output?public class InitTest { public static

2. What will this program output?public class Oblzm { public static

3. What will this program output?public class Oblzm { public static

4. What will this program output?public class Oblzm { public static

Constant Declarationfinal modifier: final int a = 42; // a =

If-Then_Else Statement Iif (boolean_expression) { statements}if (boolean_expression) { statements} else { statements}*Infopulse Training

If-Then_Else Statement IIif (boolean_expression) { statements;} else if (boolean_expression) { statements;} else if

If-Then-Else Exampleint a = 10;if (a > 0) { System.out.println("Positive");}else if (a

Switch Statementswitch(integral-expression) { case integer-value1 : statements; case integer-value2 :

Switch Examplechar c = ’b’;switch(c) { case ’a’: case ’e’: case

Switch Statement ExpressionsYou can use enumerations as switch expression and case

While and Do-While Statementwhile (boolean_expression) { statements;}do { statements;} while (boolean_expression);*Infopulse

While Exampledouble a = 100.; while (a >= 1) { System.out.println(a);

Do-While Exampledouble a = 0.5; do { System.out.println(a); a /= 2.;

For Statementfor (initialization; Boolean-expression; step) { statements;}*Infopulse Training Center

For Examplesfor (int i = 10, k = 20; i <

Break and Continue Statementsbreak quits the loop without executing the rest

Use Break with a LabelL: for … { for…{ break L;

Exercise 2.2.1.Find and print all divisors of a given natural number

Exercise 2.2.1.See 221Divisors project for the full text.*Infopulse Training Center

Exercise 2.2.2.Find and print all prime divisors of a given natural

Exercise 2.2.3.Find sum of an infinite row for a given xCompare

Похожие презентации

Comments
/* . . . */ - multi line comment
// .

How to Use Comments
Comments should be used to give overviews of

Variables
Variables declaration: int k;
double x = 2.1;
Local variable should be

1. What will this program output?
public class InitTest {
public static

2. What will this program output?
public class Oblzm {
public static

3. What will this program output?
public class Oblzm {
public static

4. What will this program output?
public class Oblzm {
public static

Constant Declaration
final modifier: final int a = 42;
// a =

If-Then_Else Statement I
if (boolean_expression) {
statements
}
if (boolean_expression) {
statements
} else {
statements
}
*
Infopulse Training

If-Then_Else Statement II
if (boolean_expression) {
statements;
} else if (boolean_expression) {
statements;
} else if

If-Then-Else Example
int a = 10;
if (a > 0) {
System.out.println("Positive");
}
else if (a

Switch Statement
switch(integral-expression) {
case integer-value1 :
statements;
case integer-value2 :

Switch Example
char c = ’b’;
switch(c) {
case ’a’:
case ’e’:
case

Switch Statement Expressions
You can use enumerations as switch expression and case

While and Do-While Statement
while (boolean_expression) {
statements;
}
do {
statements;
} while (boolean_expression);
*
Infopulse

While Example
double a = 100.;
while (a >= 1) {
System.out.println(a);

Do-While Example
double a = 0.5;
do {
System.out.println(a);
a /= 2.;

For Statement
for (initialization; Boolean-expression; step) {
statements;
}
*
Infopulse Training Center

For Examples
for (int i = 10, k = 20; i <

Break and Continue Statements
break quits the loop without executing the rest

Use Break with a Label
L: for … {
for…{
break L;

Exercise 2.2.1.
Find and print all divisors of a given natural number

Exercise 2.2.1.
See 221Divisors project for the full text.
*
Infopulse Training Center

Exercise 2.2.2.
Find and print all prime divisors of a given natural

Exercise 2.2.3.
Find sum of an infinite row for a given x
Compare