Flow control refers to the process of directing the sequence of execution of statements in a program. In Java, there are several flow control statements that allow you to control the flow of execution in your program. The main flow control statements in Java are:
-
Conditional statements:
if,else if, andelsestatements are used to execute a block of code based on a certain condition. - Switch statement:
switchstatement is used to execute one of several possible blocks of code, based on the value of a single expression. -
Looping statements:
for,while, anddo-whilestatements are used to repeat a block of code a certain number of times or until a certain condition is met. -
Jump statements:
break,continue, andreturnstatements are used to alter the normal flow of execution in a program.
Here’s an example program that demonstrates the use of these flow control statements:
public class FlowControlExample {
public static void main(String[] args) {
int x = 5;
if (x > 10) {
System.out.println("x is greater than 10");
} else if (x > 5) {
System.out.println("x is greater than 5 but less than or equal to 10");
} else {
System.out.println("x is less than or equal to 5");
}
for (int i = 1; i <= 10; i++) {
if (i == 5) {
continue;
}
if (i == 8) {
break;
}
System.out.println(i);
}
int i = 1;
while (i <= 5) {
System.out.println(i);
i++;
}
int j = 1;
do {
System.out.println(j);
j++;
} while (j <= 5);
int score = 80;
switch (score) {
case 90:
System.out.println("Grade A");
break;
case 80:
System.out.println("Grade B");
break;
case 70:
System.out.println("Grade C");
break;
default:
System.out.println("Grade D");
}
}
}
This program demonstrates how the different flow control statements work in Java. Depending on the value of x, the program uses conditional statements to execute different blocks of code. The program also uses looping statements to repeat blocks of code a certain number of times or until a certain condition is met. Finally, the program uses a switch statement to execute one of several possible blocks of code, based on the value of a single expression.
Entry control loop vs Exit control loop
Here’s a table summarizing the differences between entry-controlled loops and exit-controlled loops:
| Entry-controlled loop | Exit-controlled loop | |
|---|---|---|
| Definition | A loop where the test condition is checked before entering the loop body. | A loop where the test condition is checked after executing the loop body. |
| Control | The loop will not execute if the test condition is false before entering the loop body. | The loop will execute at least once before checking the test condition. |
| Syntax | while (testCondition) { // loop body } |
do { // loop body } while (testCondition); |
| Examples | while (i < 10) { // loop body } |
do { // loop body } while (i < 10); |
| Advantages | Test condition is evaluated first, which can save time if the condition is false. | Loop body is guaranteed to execute at least once, which can be useful in some scenarios. |
| Disadvantages | Loop body may not execute at all if the test condition is false initially. | Test condition is evaluated after executing the loop body, which can lead to unnecessary iterations. |