ICSE Class 9 Computer Applications
8. Iterative Constructs in java
01 Defination
Iterative statements allow a set of instructions to be performed repeatedly until a certain condition is fulfilled. The iterative statements are also called as loops or looping statements.
Java loop statement has 4 parts:
-
Initialization sets a loop control variable to an initial value.
-
Condition/test expression is a Boolean expression that tests the loop control variable. If condition is true, the loop continues to iterate. If condition is false, the loop terminates.
-
Update expression determines how the loop control variable is changed each time the loop iterates.
-
Body of the Loop The statements executed repeatedly whenever the condition is true.
02 Types of looping statement
entry controlled ( for , while ) – the condition is checked before entering the loop.
exit controlled ( do while ) – the condition is checked before exiting the loop
Note : do while loop is removed for this exam
03 Syntax of each loop
Syntax of for loop
for (initialization; testExpression; update)
{
// statements inside loop's body
}
Syntax of while loop
while (testExpression)
{
// statements inside loop's body
}
04 Programs
/* Program to display numbers 1 to 10 using for loop */
class forEg
{
public static void main(String args[])
{
int i;
for(i=1;i<=10;i++)
{
System.out.println(i);
}
}
}
/* Program to display numbers 1 to 10 using while loop */
class whileEg
{
public static void main(String args[])
{
int i=1;
while(i<=10)
{
System.out.println(i);
i++;
}
}
}
05 jump statements
While working with loops, it is sometimes desirable to skip some statements inside the loop or terminate the loop immediately without checking the test expression.
In such cases, break and continue statements are used.
The break statement in Java terminates the loop immediately, and the control of the program moves to the next statement following the loop.
The continue statement in Java skips the current iteration of a loop (for, while, do...while, etc) and the control of the program moves to the end of the loop. And, the test expression of a loop is evaluated.
/* Program for break statement */
class breakEg
{
public static void main(String args[])
{
for(int i=1;i<=5;i++)
{
if(i==1)
break;
System.out.println(i);
}
}
}
/* Program for continue statement */
class continueEg
{
public static void main(String args[])
{
for(int i=1;i<=5;i++)
{
if(i==2)
continue;
System.out.println(i);
}
}
}
06 Need of loops
Thus the need of loops is to repeat the same, or similar, code a number of times.