Understanding Selection Statements in Java Programming

Ella Nadine

11/30/2025

Computer Science / Programming

Selection statements Java programming

118

•

Nov 30, 2025

•

40 pages

Understanding Selection Statements in Java Programming

Ella Nadine

@nadenden

Ready to master programming decisions? In this unit, we'll explore... Show more

1 / 10

Selections

Selection statements are the decision-makers in your code. They allow programs to choose different paths based on whether certain conditions are true or false. Without selections, programs would just execute instructions in sequence without any ability to respond to different situations.

Think of selection statements as forks in a road – they direct your program which way to go based on the conditions you specify.

Boolean Data Type

The Boolean data type is the foundation of all decision-making in programming. It can hold only two values: true or false. Boolean variables store the results of comparisons and logical operations.

Here's how to create Boolean variables:

boolean isRaining = true;
boolean hasHomework = false;
boolean isTeenager = (age >= 13 && age <= 19);

Quick Tip: Boolean values are perfect for representing conditions that are either "yes" or "no" - like whether a user is logged in, if a number is positive, or if homework is completed.

The value of a Boolean can come directly from assignments $true/false$ or from evaluating expressions like comparisons.

Comparison Operators

Comparison operators let you compare values and create Boolean results. These are the tools that help your program make decisions based on data.

Operator	Name	Example	Result
<	less than	radius < 0	false
<=	less than or equal to	radius <= 0	false
>	greater than	radius > 0	true
>=	greater than or equal to	radius >= 0	true
==	equal to	radius == 0	false
!=	not equal to	radius != 0	true

Remember that == (double equals) is for comparing values, while = (single equals) is for assigning values. Mixing these up is one of the most common programming mistakes!

One-Way If Statements

A one-way if statement executes code only when a condition is true. If the condition is false, the program simply skips over the code block and continues.

if (boolean-expression) {
    statement(s);  // Only runs if condition is true
}

The code inside the curly braces is called a "block" and runs as a single unit. When the condition evaluates to true, all statements inside this block will execute. If the condition is false, the program skips the entire block.

Remember: The parentheses around the boolean expression are required, but the curly braces are optional if there's only one statement inside the block.

How If Statements Work

If statements work like checkpoints in your code. When the program reaches an if statement, it evaluates the condition and makes a decision.

When the condition is true:

int test = 5;
if (test < 10) {
    // This code runs since 5 < 10 is true
}
// Code continues here after the if block

When the condition is false:

int test = 5;
if (test > 10) {
    // This code is skipped since 5 > 10 is false
}
// Program jumps directly here

For example, you could check if a circle's radius is valid before calculating its area:

if (radius >= 0) {
    area = radius * radius * PI;
    System.out.println("The area is " + area);
}

Two-Way If Statements

A two-way if statement $if-else$ provides two alternative paths for your code. It executes one block if the condition is true and a different block if the condition is false.

if (boolean-expression) {
    statements-for-true-case;
} else {
    statements-for-false-case;
}

This is perfect for binary decisions - like whether a number is positive or negative, or if a student passed or failed a test.

Pro Tip: Two-way if statements ensure that exactly one of the two code blocks will always execute - never both and never neither!

How If-Else Works

If-else statements are like forks in the road - your program must go one way or the other.

When the condition is true:

int test = 5;
if (test < 10) {
    // This code runs
} else {
    // This code is skipped
}

When the condition is false:

int test = 5;
if (test > 10) {
    // This code is skipped
} else {
    // This code runs
}

For example, validating a circle's radius with feedback:

if (radius >= 0) {
    area = radius * radius * PI;
    System.out.println("The area is " + area);
} else {
    System.out.println("Negative input");
}

Nested If Statements

You can place if statements inside other if statements to create more complex decision paths. This is called nesting and allows you to create multi-level decision trees.

if (Boolean_expression1) {
    // Executes when expression1 is true
    if (Boolean_expression2) {
        // Executes when both expressions are true
    }
}

Nested if statements are helpful when a second decision depends on the outcome of the first decision. Think of it as asking a series of questions before taking action.

Make It Clear: When using nested if statements, proper indentation is crucial for readability. Each level of nesting should be clearly indented to show the structure of your code.

Nested If Examples

Here's a simple example using nested if statements:

public class Test {
    public static void main(String args[]) {
        int x = 30;
        int y = 10;
        
        if (x == 30) {
            if (y == 10) {
                System.out.println("X = 30 and Y = 10");
            }
        }
    }
}

And a more practical example that finds the largest of three numbers:

double n1 = -1.0, n2 = 4.5, n3 = -5.3;
double largestNumber = 0;

if (n1 >= n2)
    if (n1 >= n3)
        largestNumber = n1;
if (n3 >= n1)
    if (n3 >= n2)
        largestNumber = n3;
if (n2 >= n1)
    if (n2 >= n3)
        largestNumber = n2;

Nested If-Else Statements

Nested if-else statements create multiple decision paths. The clearest way to write complex conditions is using the else if structure:

if (condition1) {
    // Executes when condition1 is true
} else if (condition2) {
    // Executes when condition1 is false but condition2 is true
} else if (condition3) {
    // Executes when both condition1 and condition2 are false but condition3 is true
} else {
    // Executes when all conditions are false
}

This structure is perfect for categorizing values into multiple ranges, like assigning letter grades based on scores or determining weight categories from BMI values.

Think Logically: When using multiple else-if branches, arrange your conditions from most specific to most general for the clearest code.

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In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

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Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀

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Elisha

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Computer Science / Programming

•

118

•

Nov 30, 2025

•

40 pages

Understanding Selection Statements in Java Programming

Ella Nadine

@nadenden

Ready to master programming decisions? In this unit, we'll explore how Java makes choices using selection statements like if, if-else, and nested conditions. These powerful tools let your programs make decisions based on different conditions, forming the backbone of program... Show more

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Selections

Think of selection statements as forks in a road – they direct your program which way to go based on the conditions you specify.

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Boolean Data Type

Here's how to create Boolean variables:

boolean isRaining = true;
boolean hasHomework = false;
boolean isTeenager = (age >= 13 && age <= 19);

Quick Tip: Boolean values are perfect for representing conditions that are either "yes" or "no" - like whether a user is logged in, if a number is positive, or if homework is completed.

The value of a Boolean can come directly from assignments $true/false$ or from evaluating expressions like comparisons.

Sign up to see the contentIt's free!

Access to all documents

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Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Comparison Operators

Comparison operators let you compare values and create Boolean results. These are the tools that help your program make decisions based on data.

Operator	Name	Example	Result
<	less than	radius < 0	false
<=	less than or equal to	radius <= 0	false
>	greater than	radius > 0	true
>=	greater than or equal to	radius >= 0	true
==	equal to	radius == 0	false
!=	not equal to	radius != 0	true

Remember that == (double equals) is for comparing values, while = (single equals) is for assigning values. Mixing these up is one of the most common programming mistakes!

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One-Way If Statements

A one-way if statement executes code only when a condition is true. If the condition is false, the program simply skips over the code block and continues.

if (boolean-expression) {
    statement(s);  // Only runs if condition is true
}

Remember: The parentheses around the boolean expression are required, but the curly braces are optional if there's only one statement inside the block.

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Access to all documents

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Join milions of students

By signing up you accept Terms of Service and Privacy Policy

How If Statements Work

If statements work like checkpoints in your code. When the program reaches an if statement, it evaluates the condition and makes a decision.

When the condition is true:

int test = 5;
if (test < 10) {
    // This code runs since 5 < 10 is true
}
// Code continues here after the if block

When the condition is false:

int test = 5;
if (test > 10) {
    // This code is skipped since 5 > 10 is false
}
// Program jumps directly here

For example, you could check if a circle's radius is valid before calculating its area:

if (radius >= 0) {
    area = radius * radius * PI;
    System.out.println("The area is " + area);
}

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Two-Way If Statements

A two-way if statement $if-else$ provides two alternative paths for your code. It executes one block if the condition is true and a different block if the condition is false.

if (boolean-expression) {
    statements-for-true-case;
} else {
    statements-for-false-case;
}

This is perfect for binary decisions - like whether a number is positive or negative, or if a student passed or failed a test.

Pro Tip: Two-way if statements ensure that exactly one of the two code blocks will always execute - never both and never neither!

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Access to all documents

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How If-Else Works

If-else statements are like forks in the road - your program must go one way or the other.

When the condition is true:

int test = 5;
if (test < 10) {
    // This code runs
} else {
    // This code is skipped
}

When the condition is false:

int test = 5;
if (test > 10) {
    // This code is skipped
} else {
    // This code runs
}

For example, validating a circle's radius with feedback:

if (radius >= 0) {
    area = radius * radius * PI;
    System.out.println("The area is " + area);
} else {
    System.out.println("Negative input");
}

Sign up to see the contentIt's free!

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Nested If Statements

You can place if statements inside other if statements to create more complex decision paths. This is called nesting and allows you to create multi-level decision trees.

if (Boolean_expression1) {
    // Executes when expression1 is true
    if (Boolean_expression2) {
        // Executes when both expressions are true
    }
}

Nested if statements are helpful when a second decision depends on the outcome of the first decision. Think of it as asking a series of questions before taking action.

Make It Clear: When using nested if statements, proper indentation is crucial for readability. Each level of nesting should be clearly indented to show the structure of your code.

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Nested If Examples

Here's a simple example using nested if statements:

public class Test {
    public static void main(String args[]) {
        int x = 30;
        int y = 10;
        
        if (x == 30) {
            if (y == 10) {
                System.out.println("X = 30 and Y = 10");
            }
        }
    }
}

And a more practical example that finds the largest of three numbers:

double n1 = -1.0, n2 = 4.5, n3 = -5.3;
double largestNumber = 0;

if (n1 >= n2)
    if (n1 >= n3)
        largestNumber = n1;
if (n3 >= n1)
    if (n3 >= n2)
        largestNumber = n3;
if (n2 >= n1)
    if (n2 >= n3)
        largestNumber = n2;

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Nested If-Else Statements

Nested if-else statements create multiple decision paths. The clearest way to write complex conditions is using the else if structure:

if (condition1) {
    // Executes when condition1 is true
} else if (condition2) {
    // Executes when condition1 is false but condition2 is true
} else if (condition3) {
    // Executes when both condition1 and condition2 are false but condition3 is true
} else {
    // Executes when all conditions are false
}

This structure is perfect for categorizing values into multiple ranges, like assigning letter grades based on scores or determining weight categories from BMI values.

Think Logically: When using multiple else-if branches, arrange your conditions from most specific to most general for the clearest code.

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Where can I download the Knowunity app?

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Stefan S

iOS user

Samantha Klich

Android user

Anna

iOS user

Thomas R

iOS user

Brad T

Android user

Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍

David K

iOS user

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

Aubrey

iOS user

Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀

Marco B

iOS user

Elisha

iOS user

Paul T

iOS user

Stefan S

iOS user

Samantha Klich

Android user

Anna

iOS user

Thomas R

iOS user

Brad T

Android user

Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍

David K

iOS user

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

Aubrey

iOS user

Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀

Marco B

iOS user

Elisha

iOS user

Paul T

iOS user

Understanding Selection Statements in Java Programming

Selections

Boolean Data Type

Comparison Operators

One-Way If Statements

How If Statements Work

Two-Way If Statements

How If-Else Works

Nested If Statements

Nested If Examples

Nested If-Else Statements

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