This document discusses conditional statements and loops in Java. It describes the if-else statement, which allows choosing between two alternatives based on a condition, and the switch statement, which allows choosing between multiple alternatives. It also discusses the different types of loops in Java - while loops, do-while loops, and for loops. Each loop type is used to repeatedly execute code based on different conditions.

1. JAVA
"WRITE ONCE, RUN ANYWHERE”
Lec--4
By: Zubair Khalid

2. Java
£ Conditional Statements and their types
£ Loops and their types

3. To check a condition and execute certain parts of code depending on whether the
condition is true or false. Such statements are called conditional, and are a form of
composite statement.
Conditional Statements
In Java there are two forms of conditional statements
£ if-else (to choose between two alternatives)
£ switch (to choose between multiple alternatives)

4. The if-else statement allows us to select between two alternatives.
if-else
if (condition )
then-statement
else
else-statement
Syntax:

5. If we have to realize a multiple-choice selection we can use several nested if-else statements. Java
has also a specific statement that can be used in specific cases to realize in a simpler way a
multiple-choice selection.
switch
switch (expression ) {
case label-1 : statements-1; break;
...
case label-n : statements-n; break;
default: default-statement;
}
Syntax:

6. Loops are used to execute a statement or set of statements multiple times
Loops
£ while Loop
£ do-while Loop
£ for loop
There are following type of loops in Java:

7. A while loop is a control flow statement that allows code to be executed repeatedly
based on a given Boolean condition. The while loop can be thought of as a
repeating if statement.
while Loop
while(condition){
Statements;
}
Syntax:

8. Unlike for and while loops, which test the loop condition at the top of the loop, the do-while
loop checks its condition at the bottom of the loop. A do-while loop is similar to a while loop,
except the fact that it is guaranteed to execute at least one time.
do-while Loop
do{
Statements;
} while(condition);
Syntax:

9. For loop is a conditional iterative statement which is used to check for
certain conditions and then repeatedly execute a block of code as long as
those conditions are met.
for Loop
for (var_initialization ; condition ; increment/decrement){
Statements;
}
Syntax: