1. Introduction
Control statements are one of the most important features of any programming language. They allow you to control the flow of execution of your program based on certain conditions or iterations. In this tutorial, you will learn how to use control statements in Java to execute different code blocks.
Java is a popular and widely used programming language that supports object-oriented, functional, and imperative paradigms. It is known for its portability, performance, and reliability. Java has a rich set of control statements that can help you create complex and dynamic programs.
Some of the questions that you will be able to answer after reading this tutorial are:
- What are control statements in Java and why are they useful?
- What are the types of control statements in Java and how to use them?
- How to use Java conditionals, such as if-else and switch-case, to execute different code blocks based on a condition?
- How to use Java loops, such as for, while, and do-while, to execute a code block repeatedly based on an iteration?
By the end of this tutorial, you will have a solid understanding of control statements in Java and how to use them effectively in your programs. You will also be able to write more concise, readable, and maintainable code using control statements.
So, let’s get started!
2. What are Control Statements in Java?
Control statements are statements that can alter the flow of execution of a program based on certain conditions or iterations. They allow you to create different paths of execution for your program, depending on the situation. Control statements are essential for creating dynamic and interactive programs that can respond to user input, handle errors, and perform complex tasks.
Java supports three types of control statements: selection statements, iteration statements, and jump statements. Each type of control statement has a different purpose and syntax. You will learn more about each type of control statement in the next section.
Some of the benefits of using control statements in Java are:
- They make your code more readable and organized by separating different code blocks.
- They increase the efficiency and performance of your program by avoiding unnecessary code execution.
- They enhance the functionality and flexibility of your program by allowing you to create different scenarios and outcomes.
Control statements are one of the most fundamental and powerful features of Java. They enable you to create logic and algorithms for your program. Without control statements, your program would be a linear and static sequence of instructions that cannot adapt to different situations.
Now that you know what control statements are and why they are useful, let’s see how to use them in Java.
3. Types of Control Statements in Java
As mentioned in the previous section, Java supports three types of control statements: selection statements, iteration statements, and jump statements. Each type of control statement has a different purpose and syntax. In this section, you will learn more about each type of control statement and how to use them in your Java programs.
Selection statements are used to execute a code block based on a condition. They allow you to create different paths of execution for your program, depending on the value of a variable or an expression. The most common selection statements in Java are the if-else statement and the switch-case statement. You will learn how to use these statements in the next section.
Iteration statements are used to execute a code block repeatedly based on an iteration. They allow you to create loops in your program, which can perform a task multiple times until a condition is met. The most common iteration statements in Java are the for loop, the while loop, and the do-while loop. You will learn how to use these loops in the following section.
Jump statements are used to transfer the control of execution to another part of the program. They allow you to break out of a loop, skip a code block, or return a value from a method. The most common jump statements in Java are the break statement, the continue statement, and the return statement. You will learn how to use these statements in the last section.
These are the three types of control statements in Java. They are very useful for creating logic and algorithms for your program. You can use them in combination with each other to create complex and dynamic programs that can handle different scenarios and outcomes. In the next sections, you will see some examples of how to use these control statements in Java.
3.1. Selection Statements
Selection statements are one of the types of control statements in Java that allow you to execute a code block based on a condition. They enable you to create different paths of execution for your program, depending on the value of a variable or an expression. Selection statements are useful for creating conditional logic and decision making in your program.
The most common selection statements in Java are the if-else statement and the switch-case statement. Both of these statements can evaluate a condition and execute a code block accordingly. However, they have different syntax and use cases. You will learn how to use these statements in the next section.
The general syntax of the if-else statement is:
if (condition) {
// code block to execute if condition is true
} else {
// code block to execute if condition is false
}
The general syntax of the switch-case statement is:
switch (expression) {
case value1:
// code block to execute if expression matches value1
break;
case value2:
// code block to execute if expression matches value2
break;
...
default:
// code block to execute if expression does not match any value
break;
}
Some of the key points to remember when using selection statements in Java are:
- The condition or expression must be a boolean value or an expression that can be evaluated to a boolean value.
- The code block can be a single statement or a group of statements enclosed in curly braces.
- The else and default clauses are optional and can be omitted if not needed.
- The break statement is used to terminate the execution of the switch-case statement and prevent it from falling through to the next case.
Selection statements are one of the most basic and essential features of Java. They allow you to create different scenarios and outcomes for your program based on certain conditions. In the next section, you will see some examples of how to use the if-else and switch-case statements in Java.
3.2. Iteration Statements
Iteration statements are another type of control statements in Java that allow you to execute a code block repeatedly based on an iteration. They enable you to create loops in your program, which can perform a task multiple times until a condition is met. Iteration statements are useful for creating repetitive and iterative logic and operations in your program.
The most common iteration statements in Java are the for loop, the while loop, and the do-while loop. All of these loops can execute a code block based on an initial value, a condition, and an update. However, they have different syntax and use cases. You will learn how to use these loops in the following section.
The general syntax of the for loop is:
for (initialization; condition; update) {
// code block to execute for each iteration
}
The general syntax of the while loop is:
while (condition) {
// code block to execute while condition is true
}
The general syntax of the do-while loop is:
do {
// code block to execute at least once
} while (condition);
Some of the key points to remember when using iteration statements in Java are:
- The initialization, condition, and update are expressions that control the iteration of the loop. The initialization is executed only once before the loop starts. The condition is evaluated before each iteration and determines whether the loop should continue or stop. The update is executed after each iteration and modifies the value of the loop variable.
- The code block can be a single statement or a group of statements enclosed in curly braces.
- The for loop is suitable for situations where you know the exact number of iterations or you want to iterate over an array or a collection.
- The while loop is suitable for situations where you do not know the exact number of iterations or you want to execute the loop until a certain condition is met.
- The do-while loop is similar to the while loop, except that it executes the code block at least once before checking the condition. It is suitable for situations where you want to perform the loop action at least once regardless of the condition.
Iteration statements are one of the most common and useful features of Java. They allow you to create loops in your program that can perform a task multiple times until a condition is met. In the next section, you will see some examples of how to use the for, while, and do-while loops in Java.
3.3. Jump Statements
Jump statements are the third type of control statements in Java that allow you to transfer the control of execution to another part of the program. They enable you to break out of a loop, skip a code block, or return a value from a method. Jump statements are useful for creating exceptions, interruptions, and exits in your program.
The most common jump statements in Java are the break statement, the continue statement, and the return statement. All of these statements can alter the normal flow of execution of a program and jump to a different point. However, they have different syntax and use cases. You will learn how to use these statements in the last section.
The general syntax of the break statement is:
break;
The general syntax of the continue statement is:
continue;
The general syntax of the return statement is:
return expression;
Some of the key points to remember when using jump statements in Java are:
- The break statement is used to terminate the execution of a loop or a switch-case statement and jump to the next statement after the loop or switch.
- The continue statement is used to skip the current iteration of a loop and jump to the next iteration.
- The return statement is used to terminate the execution of a method and return a value to the caller.
- The expression in the return statement must match the return type of the method. If the method has a void return type, the expression can be omitted.
Jump statements are one of the most advanced and powerful features of Java. They allow you to create exceptions, interruptions, and exits in your program that can handle different situations and outcomes. In the next section, you will see some examples of how to use the break, continue, and return statements in Java.
4. Java Conditionals: if-else and switch-case
In this section, you will learn how to use the if-else and switch-case statements in Java. These are the most common selection statements in Java that allow you to execute a code block based on a condition. You will see some examples of how to use these statements to create different paths of execution for your program, depending on the value of a variable or an expression.
The if-else statement is used to execute a code block if a condition is true, and another code block if the condition is false. The condition must be a boolean value or an expression that can be evaluated to a boolean value. The code block can be a single statement or a group of statements enclosed in curly braces. The else clause is optional and can be omitted if not needed.
For example, suppose you want to write a program that checks if a number is even or odd. You can use the if-else statement to do that, as shown below:
// declare a variable and assign a value
int number = 10;
// check if the number is even or odd
if (number % 2 == 0) {
// code block to execute if the condition is true
System.out.println("The number is even.");
} else {
// code block to execute if the condition is false
System.out.println("The number is odd.");
}
The output of this program is:
The number is even.
The switch-case statement is used to execute a code block based on the value of an expression. The expression must be an integer, a character, a string, or an enum. The code block can be a single statement or a group of statements enclosed in curly braces. The break statement is used to terminate the execution of the switch-case statement and prevent it from falling through to the next case. The default clause is optional and can be omitted if not needed.
For example, suppose you want to write a program that prints the name of a month based on a number. You can use the switch-case statement to do that, as shown below:
// declare a variable and assign a value
int month = 3;
// print the name of the month based on the number
switch (month) {
case 1:
// code block to execute if the expression matches 1
System.out.println("January");
break;
case 2:
// code block to execute if the expression matches 2
System.out.println("February");
break;
case 3:
// code block to execute if the expression matches 3
System.out.println("March");
break;
...
default:
// code block to execute if the expression does not match any case
System.out.println("Invalid month");
break;
}
The output of this program is:
March
These are some examples of how to use the if-else and switch-case statements in Java. You can use these statements to create different scenarios and outcomes for your program based on certain conditions. In the next section, you will learn how to use the for, while, and do-while loops in Java.
4.1. The if-else Statement
The if-else statement is one of the most common selection statements in Java that allows you to execute a code block if a condition is true, and another code block if the condition is false. The condition must be a boolean value or an expression that can be evaluated to a boolean value. The code block can be a single statement or a group of statements enclosed in curly braces. The else clause is optional and can be omitted if not needed.
To use the if-else statement in Java, you need to follow these steps:
- Write the keyword if followed by a pair of parentheses.
- Inside the parentheses, write the condition that you want to check. The condition can be a variable, a comparison, a logical operation, or any expression that returns a boolean value.
- After the parentheses, write a pair of curly braces. Inside the curly braces, write the code block that you want to execute if the condition is true.
- Optionally, write the keyword else followed by another pair of curly braces. Inside the curly braces, write the code block that you want to execute if the condition is false.
Here is an example of how to use the if-else statement in Java:
// declare a variable and assign a value
int age = 18;
// check if the age is greater than or equal to 18
if (age >= 18) {
// code block to execute if the condition is true
System.out.println("You are an adult.");
} else {
// code block to execute if the condition is false
System.out.println("You are a minor.");
}
The output of this program is:
You are an adult.
The if-else statement is very useful for creating conditional logic and decision making in your program. You can use it to execute different code blocks based on different conditions. You can also nest multiple if-else statements inside each other to create more complex scenarios and outcomes.
In the next section, you will learn how to use the switch-case statement in Java.
4.2. The switch-case Statement
The switch-case statement is another selection statement in Java that allows you to execute a code block based on the value of an expression. The expression must be an integer, a character, a string, or an enum. The code block can be a single statement or a group of statements enclosed in curly braces. The break statement is used to terminate the execution of the switch-case statement and prevent it from falling through to the next case. The default clause is optional and can be omitted if not needed.
To use the switch-case statement in Java, you need to follow these steps:
- Write the keyword switch followed by a pair of parentheses.
- Inside the parentheses, write the expression that you want to evaluate. The expression can be a variable, a literal, a method call, or any expression that returns an integer, a character, a string, or an enum.
- After the parentheses, write a pair of curly braces. Inside the curly braces, write one or more case clauses and optionally a default clause.
- For each case clause, write the keyword case followed by a constant value that matches the type of the expression. Then write a colon and the code block that you want to execute if the expression matches the value. At the end of the code block, write the keyword break followed by a semicolon to exit the switch-case statement.
- Optionally, for the default clause, write the keyword default followed by a colon and the code block that you want to execute if the expression does not match any case. The default clause can be placed anywhere inside the curly braces, but it is usually placed at the end. The break statement is not required for the default clause, but it is recommended to avoid confusion.
Here is an example of how to use the switch-case statement in Java:
// declare a variable and assign a value
char grade = 'A';
// print the feedback based on the grade
switch (grade) {
case 'A':
// code block to execute if the expression matches 'A'
System.out.println("Excellent!");
break;
case 'B':
// code block to execute if the expression matches 'B'
System.out.println("Good job!");
break;
case 'C':
// code block to execute if the expression matches 'C'
System.out.println("You can do better.");
break;
case 'D':
// code block to execute if the expression matches 'D'
System.out.println("You need to work hard.");
break;
case 'F':
// code block to execute if the expression matches 'F'
System.out.println("You failed.");
break;
default:
// code block to execute if the expression does not match any case
System.out.println("Invalid grade.");
break;
}
The output of this program is:
Excellent!
The switch-case statement is very useful for creating multiple paths of execution for your program based on the value of an expression. You can use it to execute different code blocks based on different cases. You can also nest switch-case statements inside each other to create more complex scenarios and outcomes.
In the next section, you will learn how to use the for, while, and do-while loops in Java.
5. Java Loops: for, while, and do-while
In this section, you will learn how to use the for, while, and do-while loops in Java. These are the most common iteration statements in Java that allow you to execute a code block repeatedly based on an iteration. You will see some examples of how to use these loops to create cycles and repetitions in your program, depending on the value of a variable or an expression.
The for loop is used to execute a code block for a fixed number of times. It consists of four parts: an initialization, a condition, an update, and a code block. The initialization is executed only once before the loop starts. The condition is checked before each iteration of the loop. The update is executed after each iteration of the loop. The code block is executed as long as the condition is true.
For example, suppose you want to write a program that prints the numbers from 1 to 10. You can use the for loop to do that, as shown below:
// declare and initialize a variable
int i;
// use a for loop to print the numbers from 1 to 10
for (i = 1; i <= 10; i++) {
// code block to execute for each iteration of the loop
System.out.println(i);
}
The output of this program is:
1 2 3 4 5 6 7 8 9 10
The while loop is used to execute a code block as long as a condition is true. It consists of two parts: a condition and a code block. The condition is checked before each iteration of the loop. The code block is executed as long as the condition is true.
For example, suppose you want to write a program that prints the numbers from 1 to 10. You can use the while loop to do that, as shown below:
// declare and initialize a variable
int i = 1;
// use a while loop to print the numbers from 1 to 10
while (i <= 10) {
// code block to execute for each iteration of the loop
System.out.println(i);
// update the variable
i++;
}
The output of this program is:
1 2 3 4 5 6 7 8 9 10
The do-while loop is similar to the while loop, except that the condition is checked after each iteration of the loop. It consists of two parts: a code block and a condition. The code block is executed at least once, regardless of the condition. The condition is checked after each iteration of the loop. The code block is executed as long as the condition is true.
For example, suppose you want to write a program that prints the numbers from 1 to 10. You can use the do-while loop to do that, as shown below:
// declare and initialize a variable
int i = 1;
// use a do-while loop to print the numbers from 1 to 10
do {
// code block to execute for each iteration of the loop
System.out.println(i);
// update the variable
i++;
} while (i <= 10);
The output of this program is:
1 2 3 4 5 6 7 8 9 10
These are some examples of how to use the for, while, and do-while loops in Java. You can use these loops to create cycles and repetitions in your program based on different iterations. You can also nest loops inside each other to create more complex patterns and sequences.
In the next section, you will learn how to use the break, continue, and return statements in Java.
5.1. The for Loop
The for loop is one of the most common iteration statements in Java that allows you to execute a code block for a fixed number of times. It consists of four parts: an initialization, a condition, an update, and a code block. The initialization is executed only once before the loop starts. The condition is checked before each iteration of the loop. The update is executed after each iteration of the loop. The code block is executed as long as the condition is true.
To use the for loop in Java, you need to follow these steps:
- Write the keyword for followed by a pair of parentheses.
- Inside the parentheses, write the initialization, the condition, and the update, separated by semicolons. The initialization is usually used to declare and assign a variable that will act as a counter for the loop. The condition is usually a comparison between the counter and a limit value. The update is usually an increment or decrement of the counter.
- After the parentheses, write a pair of curly braces. Inside the curly braces, write the code block that you want to execute for each iteration of the loop.
Here is an example of how to use the for loop in Java:
// use a for loop to print the numbers from 1 to 10
for (int i = 1; i <= 10; i++) {
// code block to execute for each iteration of the loop
System.out.println(i);
}
The output of this program is:
1 2 3 4 5 6 7 8 9 10
The for loop is very useful for creating cycles and repetitions in your program based on a fixed number of times. You can use it to perform a task multiple times with a simple and concise syntax. You can also use different variables, conditions, and updates to create different patterns and sequences.
In the next section, you will learn how to use the while loop in Java.
5.2. The while Loop
The while loop is another iteration statement in Java that allows you to execute a code block as long as a condition is true. It consists of two parts: a condition and a code block. The condition is checked before each iteration of the loop. The code block is executed as long as the condition is true.
To use the while loop in Java, you need to follow these steps:
- Write the keyword while followed by a pair of parentheses.
- Inside the parentheses, write the condition that you want to check. The condition can be a variable, a comparison, a logical operation, or any expression that returns a boolean value.
- After the parentheses, write a pair of curly braces. Inside the curly braces, write the code block that you want to execute for each iteration of the loop.
Here is an example of how to use the while loop in Java:
// declare and initialize a variable
int i = 1;
// use a while loop to print the numbers from 1 to 10
while (i <= 10) {
// code block to execute for each iteration of the loop
System.out.println(i);
// update the variable
i++;
}
The output of this program is:
1 2 3 4 5 6 7 8 9 10
The while loop is very useful for creating cycles and repetitions in your program based on a condition that is not known in advance. You can use it to perform a task until a certain condition is met, such as getting user input, reading a file, or checking a sensor. You can also use different variables, conditions, and updates to create different patterns and sequences.
In the next section, you will learn how to use the do-while loop in Java.
5.3. The do-while Loop
The do-while loop is similar to the while loop, except that the condition is checked after each iteration of the loop. It consists of two parts: a code block and a condition. The code block is executed at least once, regardless of the condition. The condition is checked after each iteration of the loop. The code block is executed as long as the condition is true.
To use the do-while loop in Java, you need to follow these steps:
- Write the keyword do followed by a pair of curly braces.
- Inside the curly braces, write the code block that you want to execute for each iteration of the loop.
- After the curly braces, write the keyword while followed by a pair of parentheses.
- Inside the parentheses, write the condition that you want to check. The condition can be a variable, a comparison, a logical operation, or any expression that returns a boolean value.
- After the parentheses, write a semicolon to end the statement.
Here is an example of how to use the do-while loop in Java:
// declare and initialize a variable
int i = 1;
// use a do-while loop to print the numbers from 1 to 10
do {
// code block to execute for each iteration of the loop
System.out.println(i);
// update the variable
i++;
} while (i <= 10);
The output of this program is:
1 2 3 4 5 6 7 8 9 10
The do-while loop is very useful for creating cycles and repetitions in your program based on a condition that is checked at the end of the loop. You can use it to perform a task at least once, even if the condition is false initially. You can also use different variables, conditions, and updates to create different patterns and sequences.
In the next section, you will learn how to use the break, continue, and return statements in Java.
6. Conclusion
In this tutorial, you have learned how to use control statements in Java to execute different code blocks based on certain conditions or iterations. You have seen some examples of how to use the if-else statement and the switch-case statement to create different paths of execution for your program. You have also seen some examples of how to use the for loop, the while loop, and the do-while loop to create cycles and repetitions in your program. You have also learned how to use the break, continue, and return statements to transfer the control of execution to another part of the program.
Control statements are one of the most important and powerful features of Java. They enable you to create logic and algorithms for your program. They make your code more readable, organized, efficient, functional, and flexible. They allow you to create complex and dynamic programs that can handle different scenarios and outcomes.
By mastering control statements in Java, you will be able to write more concise, readable, and maintainable code. You will also be able to solve more challenging and interesting problems with your Java programs.
We hope you enjoyed this tutorial and learned something new and useful. If you have any questions or feedback, please feel free to leave a comment below. Thank you for reading and happy coding!
