Chapter 1 Nested Control Structures

Fundamentals of (Java) Programming
Khirulnizam Abd Rahman
0129034614 (WhatsApp/SMS)
Khirulnizam@gmail.com
KERUL.net

About Khirulnizam
Lecturer of Computer Science, Faculty of Information Science and
Technology, Selangor International Islamic University College
(KUIS) – since 2000.
Codes in blog.kerul.net
Programming background: C, Java, PHP.
Apps in Google Play
M-Mathurat – 200K ( bit.ly/m-mathurat )
Peribahasa Dictionary – 20K ( bit.ly/pbahasa)
mDictionary – open-sourced ( bit.ly/m-dictionary )
Hijrah Rasul – bit.ly/hijrah-rasul
SmartSolat – bit.ly/smartsolat
Apps in Windows Store
Hijrah Rasul – bit.ly/hijrah-en
Peribahasa Dictionary
2 http://blog.kerul.net 11/28/14

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
3 Program Design, 3e

Assessment

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

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
statement3 Fcondition T
statement2
Statement-n
End

Repetition Structure
Same statement is repeated in a number of times depending
on one or more condition.
start
statement1
statement2
condition
Statement-n
End
T
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 Expression
Evaluate 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

Logical Expression
Evaluate 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)
F
System.out.println(“GOOD!!”);
System.out.println(“THANK YOU”);
Output :
THANK YOU
Mark = 34

If (condition)
statement1;
statement2;
T F
If (mark > 50)
Mark = 60
T
Output :
GOOD!!
THANK YOU

If (mark > 50){
Mark = 45
F
System.out.println(“GRAGE = A!!”);
}
Output :
THANK YOU

If (mark > 50){
Mark = 60
T
System.out.println(“GRAGE = A!!”);
}
Output :
GOOD!!
GRADE = A
THANK YOU

If Statement : Two-Way IF
The Syntax
if (condition)
statement1;
else
statement2;
statement3;
Only one statement
for each

The Syntax
if (score > 50)
F Mark = 34
else
System.out.println(“BAD!!”);
Output :
BAD!!
THANK YOU

The Syntax
if (score > 50)
T Mark = 60
else
Output :
GOOD!!
THANK YOU

The Syntax
if (condition)
{
statement1;
statement2;
}
else
{
Statement3;
Statement4;
}
Statement5;
More than one
statement

The Syntax
if (score > 50){
T Mark = 60
System.out.println(“GRADE = A!!”);}
else
Output :
GOOD!!
GRADE = A
THANK YOU

The Syntax
if (score > 50){
F Mark = 40
System.out.println(“GRADE = A!!”);}
else
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

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

Output :
Grade = F
if (mark > 70)
grade = “A”;
F Mark = 34?
F
grade = “B”;
mark = mark + 3;}
F
grade = “C”;
grade = “D”;
else {
grade = “F”
T
System.out.println(“Grade = “ + grade);

if (mark > 70)
grade = “A”;
F Mark = 65?
T
grade = “B”;
mark = mark + 3;}
grade = “C”;
grade = “D”;
else {
grade = “F”
Output :
Grade = B
System.out.println(“Grade = “ + grade);

Selection Structure : Switch
switch(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 : Switch
switch(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 = 2
F
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

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
Good bye
System.out.println("Good bye");
Nested if statement
No output given

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
false inner if
messageBox.show
("You did not
pass");
40
messageBox.show
("You did not
pass");
false
testScore >= 70
?
testScore >= 70
?
messageBox.show
("You did pass");
messageBox.show
("You did pass");
true
studentAge < 10
?
studentAge < 10
?
true
messageBox.show
("You did a great
job");
messageBox.show
("You did a great
job");

Nested if-else Statements
An if-else statement can contain any sort of statement
within it.
In particular, it can contain another if-else statement.
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
Syntax
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.
Score Grade
90 <= score A
80 <= score < 90 B
70 <= score < 80 C
60 <= score < 70 D
Score < 60 F
Example:
If student score is 99 then display the grade which is A to student.

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

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 loop
prints the four rows and in each row, the inner loop
prints the 9 columns.

Nested Loops (cont.)
The table shows the relationship between the row and
column variables needed to print the following triangular
pattern:
# # # # #
# # # #
# # #
# #
#
• You could use the following nested for loop.
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
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

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.
54

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(“”);
RENNI
}
RETUO

Chapter 1 Nested Control Structures

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