7. Flow Control in Java: if, else, switch, loops
Flow control is one of the fundamental concepts in Java programming, as it allows the program to make decisions and execute code repetitions according to specific conditions. In this chapter, we will explore the main flow control elements: if, else, switch, and the for loops , while and do-while.
If-else conditional
if is the most basic control structure. It tests a condition and, if that condition is true (true), executes a block of code. Otherwise, the program continues execution after the if block. The else structure, which is optional, allows you to define a block of code that will be executed if the if condition is not true.
if (condition) {
// Block of code that will be executed if condition is true
} else {
// Block of code that will be executed if condition is false
}
You can chain multiple if-else statements to test multiple conditions.
if (condition1) {
// Code block for condition1 true
} else if (condition2) {
// Code block for condition2 true
} else {
// Code block if none of the previous conditions are true
}
Switch structure
The switch is a way to replace multiple if-else when you want to compare the same variable with different values. The variable is tested against a series of values (case) and when it finds a match, it executes the block of code associated with that value. The break keyword is used to exit the switch after executing a block of code. The default is optional and defines the code to be executed if no case matches.
switch (variable) {
case value1:
// Code for value1
break;
case value2:
// Code for value2
break;
// ...
default:
// Code if no case matches
}
Loops: for, while and do-while
Loops allow you to execute a block of code repeatedly as long as a condition is true. There are three main types of loops in Java:
- for: Generally used when the number of iterations is known. The
forsyntax includes the initialization, loop continuation condition, and increment or decrement expression all on a single line. - while: Executes a block of code while a condition is true. The condition is evaluated before the code block is executed, which means the block may never be executed if the condition is false from the beginning.
- do-while: Similar to
while, but the condition is evaluated after the code block has been executed, ensuring that the block is executed at least once.< /li>
Loop for
for (initialization; condition; increment) {
// Code to be repeated
}
Example:
for (int i = 0; i < 10; i++) {
System.out.println("i = " + i);
}
Loop while
while (condition) {
// Code to be repeated
}
Example:
int i = 0;
while (i < 10) {
System.out.println("i = " + i);
i++;
}
Do-while loop
of {
// Code to be repeated
} while (condition);
Example:
int i = 0;
of {
System.out.println("i = " + i);
i++;
} while (i < 10);
Advanced Flow Control
In addition to the basic structures, there are commands like break and continue that offer additional control over loops. break is used to exit a loop immediately, while continue skips to the next iteration of the loop.
Use of break
for (int i = 0; i < 10; i++) {
if (i == 5) {
break; // Exit the loop when i is equal to 5
}
System.out.println("i = " + i);
}
Use of continue
for (int i = 0; i < 10; i++) {
if (i % 2 == 0) {
continues; // Skip to next iteration if i is even
}
System.out.println("i = " + i);
}
It is important to note that excessive use of break and continue can make code difficult to read and maintain. Therefore, you should use them with caution and only when they actually improve the clarity or efficiency of the code.
Conclusion
Flow control is essential for creating dynamic and interactive programs in Java. Understand and efficiently use theif-else, switch structures and the for, while and do-while loops > allows you to write code that responds to different conditions and performs repetitive tasks effectively. Constant practice of these concepts is essential to becoming a competent Java programmer.
