chapter 1 nested control structures

Khirulnizam Abd Rahman

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KERUL.net

Fundamentals of (Java)

Programming

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About Khirulnizam Lecturer of Computer Science, Faculty of Information

Science and Technology, Selangor International Islamic University College (KUIS) – since 2000.

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Programming background: C, Java, PHP.

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Course Synopsis

This course is the continuation of the previous course

(Algorithm and Problem Solving). It introduces

complex flow control, method, array, class design, file

and file I/O.

Objectives: At the end of this course, students

should be able to;

write and apply complex control structure.

create and invoke methods in programs.

declare, create and apply arrays and classes.

retrieve from and write data into another file.Java Programming: From Problem Analysis to

Program Design, 3e3

Assessment

Java Programming: From Problem Analysis to

Program Design, 3e4

Main Text

Liang Y. Daniel. Introduction to Java

Programming, Eight Edition, 2011, Pearson

F. Joyce. Java Programming, 6th Edition, 2011,

Course Technology

Tool: JDK & Eclipse Java IDE

Java Programming: From Problem Analysis to

Program Design, 3e5

Control Structure I

Control Structures A computer can process a program in three(3)

ways :

Sequence (line by line)

Selection or choice (branch)

Repetition

Sequence Structure Start at the beginning and follows the statement

in order.

start

statement1

statement2

Statement-n

End

…

Selection Structure Statement executions is depending on one or

more condition

start

statement1

statement2

Statement-n

End

conditionstatement3 TF

Repetition Structure Same statement is repeated in a number of times

depending on one or more condition.

start

statement1

statement2

Statement-n

End

conditionT

F

Conditional Expression Consider the following statement

If (score is greater than or equal to 90)

grade is A

If (temperature is greater than 50)

display “Its Hot”

Conditional

expression

Grade is A only if

score >=90

Display Its Hot

only if the

temperature > 50

Logical Expression

Write the logical expression for the following

1. yourAge is greater than 50.

2. The value of myAge is not 0.

3. y is between 20 and 100

4. height is between 1.5 and 2.0.

Logical Expression

Use Logical & comparison operator to construct

the

logical expression

1. yourAge > 50

2. myAge != 0

3. y > 20 && y <100

4. height > 1.5 && height < 2.0.

Logical ExpressionEvaluate the following expression. Given x is 5

and y is 200.

1. x != 12

2. y < 100

3. x == 5

4. y == x*40

5. x >=5 && x <=5

6. y == 200 || y ==100

7. x == 10 || x != 5

Selection Structure

There are 2 types of Selection

Structure

If statement

Switch statement

Selection Structure – If Statement

There are 3 types of if statement

One-way selection : if

Two-way selection : if - else

Multiple-way selection : if – else if

- else

If Statement : One-Way IF The Syntax

If (condition)

statement;

if (condition)

{

statement1;

statement2;

}

Only one

statement

More than

one

statement

If Statement : One-Way If

If (condition)

statement1;

statement2;

T F

If (mark > 50)

System.out.println(“GOOD!!”);

System.out.println(“THANK YOU”);

F

Output :

THANK YOU

Mark = 34


If (condition)

statement1;

statement2;

T F

If (mark > 50)



Mark = 60T

Output :

GOOD!!

THANK YOU


If (mark > 50){


System.out.println(“GRAGE = A!!”);

}


Mark = 45F

Output :

THANK YOU


If (mark > 50){


System.out.println(“GRAGE = A!!”);

}


Mark = 60T

Output :

GOOD!!

GRADE = A

THANK YOU

If Statement : Two-Way IF The Syntax

if (condition)

statement1;

else

statement2;

statement3;

Only one statement

for each


if (score > 50)


else

System.out.println(“BAD!!”);


Mark = 34F

Output :

BAD!!

THANK YOU


if (score > 50)


else



Mark = 60T

Output :

GOOD!!

THANK YOU


if (condition)

{

statement1;

statement2;

}

else

{

Statement3;

Statement4;

}

Statement5;

More than one

statement


if (score > 50){


System.out.println(“GRADE = A!!”);}

else



Mark = 60T

Output :

GOOD!!

GRADE = A

THANK YOU


if (score > 50){


System.out.println(“GRADE = A!!”);}

else



Mark = 40F

Output :

BAD!!

THANK YOU

If Statement : Multiple-Way IF The Syntax

if (condition)

statement1;

else if (condition){

statement2;

statement3;}

else if (condition)

statement4;

else if (condition)

statement5;

else {

statement6;

statement7;}

Use braces if there

are more than one

statement in a group

If Statement : Multiple-Way IF The Syntax

if (mark > 70)

grade = “A”;

else if (mark > 60 && mark <= 70){

grade = “B”;

mark = mark + 3;}

else if (mark > 50 && mark <=60)

grade = “C”;


grade = “D”;

else {

grade = “F”

message = “FAIL!!!”}

Don’t use

60 < mark <=70 x

If Statement : Multiple-Way IF

if (mark > 70)

grade = “A”;


grade = “B”;

mark = mark + 3;}


grade = “C”;


grade = “D”;

else {

grade = “F”


System.out.println(“Grade = “ + grade);

Mark = 34?F

F

F

T

Output :

Grade = F

If Statement : Multiple-Way IF

if (mark > 70)

grade = “A”;


grade = “B”;

mark = mark + 3;}


grade = “C”;


grade = “D”;

else {

grade = “F”


System.out.println(“Grade = “ + grade);

Mark = 65?F

T

Output :

Grade = B

Selection Structure : Switchswitch(expression) { //start switch

case value1:statement1;break;

case value2:statement2;statement3;break;

case value3:statement4;break;

…default:

statement-n;

} // end switch

use colon

not semicolon

Selection Structure : Switchswitch(month) { //start switch

case 1:

Name = “January”;

break;

case 2:

name = “February”;

break;

case 3:

name = “March”;

break;

…

default:

name = “ Not available”;

} // end switch

System,out.println(“Month = “ + name);

Month = 2F

T

C1 - COMPLEX FLOW

CONTROL

FUNDAMENTALS OF PROGRAMMING

DTCP 2023

NESTED IF STATEMENT

SYNTAX

if (Boolean_Expression_1)


Statement_1)

else

Statement_2

Nested Statements

Subtly different forms

First Form

if (a > b)

{

if (c > d)

e = f

}

else

g = h;

Second Form

if (a > b)

if (c > d)

e = f

else

g = h;

// oops

Nested if statement

What is the output? Any difference???if ( x < y)

if (x < z)

System.out.println("Hello");

else

System.out.println("Good bye");

if ( x < y){

if (x < z)

System.out.println("Hello");

}else

System.out.println("Good bye");

No output

given

Good bye

The Nested-if Statement

The then and else block of an if statement can contain any valid statements, including other if statements. An if statement containing another if statement is called a nested-if statement.

39

if (testScore >= 70) {

if (studentAge < 10) {

System.out.println("You did a great job");

} else {

System.out.println("You did pass"); //test score >= 70

} //and age >= 10

} else { //test score < 70

System.out.println("You did not pass");

}

Control Flow of Nested-if Statement

40

messageBox.show

("You did not

pass");

falseinner if

messageBox.show

("You did pass");

false

testScore >=

70 ?

true

studentAge <

10 ?

messageBox.show

("You did a great

job");

true

Nested if-else Statements

An if-else statement can contain any sort of

statement within it.

In particular, it can contain another if-elsestatement. An if-else may be nested within the "if" part.

An if-else may be nested within the "else" part.

An if-else may be nested within both parts.

Nested Statements

Syntaxif (Boolean_Expression_1)


Statement_1)

else

Statement_2)

else


Statement_3)

else

Statement_4);

Nested Statements

Each else is paired with the nearest unmatched

if.

If used properly, indentation communicates which if goes with which else.

Braces can be used like parentheses to group

statements.

TRACE THE OUTPUT

public class test{

public static void main(String[] args){

int a=4;

for (int i=1; i<a;i++ ){

for (int j=1; j<=i;j++ ){

System.out.print("*");

}

System.out.println("");

}

}

*

**

***

EXERCISE Construct a simple program that apply nested if else

statement follow the rules given.

Example:

If student score is 99 then display the grade which is A to student.

Score Grade

90 <= score A

80 <= score < 90 B

70 <= score < 80 C

60 <= score < 70 D

Score < 60 F

46

Nested if Statements The statement executed as a result of an if

statement or else clause could be another if

statement

These are called nested if statements

See MinOfThree.java (page 227)

An else clause is matched to the last unmatched

if (no matter what the indentation implies)

Braces can be used to specify the if statement

to which an else clause belongs

MinOfThree.java

Nested Control Structures

for loops can be found within other for loops

47

Example 1

for (int i = 1; i <= 5; i++)

{

for (int j = 1; j <= i; j++)

System.out.print(" *");

System.out.println();

}

48

Output:

***************

Example 2

What will be the value of after each of the

following nested loops is executed?

for (int i = 1; i < 4; i++){

for (int j = 1; j < 4-i; j++){

System.out.print(" *");

} System.out.println();

}

49

Output:

**

*

Example 3

What will be the value of after each of the

following nested loops is executed?

int sum = 0;

for (int i = 0; i<=2; i++)

{ for (int j = 0; j<=2; j++)

{ sum = sum + i;

}

}System.out.println(sum);

50

Output:

9

Example 4

What does the following program segment print?

for (int f = 0; f < 3; ++f){

for (int g = 0; g < 2; ++g){

System.out.print(f);

System.out.print(g);

}

}

51

Output:

000110112021

Nested Loops Suppose you wanted to print the following

table:

for (int row = 1; row <= 4; row++) { // For each of 4 rows

for (int col = 1; col <= 9; col++) // For each of 9 columns

System.out.print(col * row + "\t"); // Print 36 numbers

System.out.println(); // Start a new row

} // for row

1 2 3 4 5 6 7 8 9

2 4 6 8 10 12 14 16 18

3 6 9 12 15 18 21 24 27

4 8 12 16 20 24 28 32 36

• You could use a nested for loop. The outer loopprints the four rows and in each row, the inner loopprints the 9 columns.

Nested Loops (cont.) The table shows the relationship between the

row and column variables needed to print the following triangular pattern:

for (int row = 1; row <= 5; row++) { // For each row

for (int col = 1; col <= 6 - row; col++) // Print the row

System.out.print('#');

System.out.println(); // And a new row

} // for row

# # # # #

# # # #

# # #

# #

#

• You could use the following nested for loop.

Row Column Bound

(6 – Row)

Number of

Symbols

1 6-1 5

2 6-2 4

3 6-3 3

4 6-4 2

5 6-5 1

54

The Nested-for Statement Nesting a for statement inside another for statement is

commonly used technique in programming.

Let’s generate the following table using nested-for statement.

55

Generating the Table

int price;

for (int width = 11; width <=20, width++){

for (int length = 5, length <=25, length+=5){

price = width * length * 19; //$19 per sq. ft.

System.out.print (“ “ + price);

}

//finished one row; move on to next row

System.out.println(“”);

}

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chapter 1 nested control structures

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