Decision Making in Java (if, if-else, switch, break, continue, jump)

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Decision-making statements in Java execute a block of code based on a condition. Decision-making in programming is similar to decision-making in real life. In programming, we also face situations where we want a certain block of code to be executed when some condition is fulfilled.

A programming language uses control statements to control the flow of execution of a program based on certain conditions. These are used to cause the flow of execution to advance and branch based on changes to the state of a program. Java provides several control statements to manage program flow, including:

• Conditional Statements: if, if-else, nested-if, if-else-if
• Switch-Case: For multiple fixed-value checks
• Jump Statements: break, continue, return

Types of Decision-Making Statements

• if
• if-else
• nested-if
• if-else-if
• switch-case
• jump – break, continue, return

The table below demonstrates various control flow statements in programming, their use cases, and examples of their syntax.

1. Java if Statement

The if statement is the most simple decision-making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e. if a certain condition is true then a block of statements is executed otherwise not. 

Syntax: 

if(condition) {

// Statements to execute if

// condition is true

}

Here, the condition after evaluation will be either true or false. if statement accepts boolean values – if the value is true then it will execute the block of statements under it. If we don’t use curly braces( {} ), only the next line after the if is considered as part of the if block For example, 

if (condition) // Assume condition is true

statement1; // Belongs to the if block

statement2; // Does NOT belong to the if block

Here’s what happens:

• If the condition is True statement1 executes.
• statement2 runs no matter what because it’s not a part of the if block

if Statement Execution Flow

The below diagram demonstrates the flow chart of an “if Statement execution flow” in programming.

Example: The below Java program demonstrates without curly braces, only the first line after the if statement is part of the if block and the rest code will be execute independently.

// Java program to illustrate 
// if statement without curly block
import java.util.*;

class Geeks {
    public static void main(String args[])
    {
        int i = 10;

        if (i < 15)
          
            // part of if block(immediate one statement
            // after if condition)
            System.out.println("Inside If block");

        // always executes as it is outside of if block
        System.out.println("10 is less than 15");

        // This statement will be executed
        // as if considers one statement by default again
        // below statement is outside of if block
        System.out.println("I am Not in if");
    }
}

Inside If block
10 is less than 15
I am Not in if

2. Java if-else Statement

The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t. But what if we want to do something else if the condition is false? Here, comes the “else” statement. We can use the else statement with the if statement to execute a block of code when the condition is false. 

Syntax: 

if(condition){

// Executes this block if

// condition is true

}else{

// Executes this block if

// condition is false

}

if-else Statement Execution flow

The below diagram demonstrates the flow chart of an “if-else Statement execution flow” in programming

Example: The below Java program demonstrates the use of if-else statement to execute different blocks of code based on the condition.

// Java program to demonstrate 
// the working of if-else statement
import java.util.*;

class Geeks {
    public static void main(String args[])
    {
        int i = 10;

        if (i < 15)
            System.out.println("i is smaller than 15");
        else
            System.out.println("i is greater than 15");
    }
}

i is smaller than 15

3. Java nested-if Statement

A nested if is an if statement that is the target of another if or else. Nested if statements mean an if statement inside an if statement. Yes, java allows us to nest if statements within if statements. i.e, we can place an if statement inside another if statement. 

Syntax: 

if (condition1) {

// Executes when condition1 is true

if (condition2)

{

// Executes when condition2 is true

}

}

nested-if Statement Execution Flow

The below diagram demonstrates the flow chart of an “nested-if Statement execution flow” in programming.

Example: The below Java program demonstrates the use of nested if statements to check multiple conditions.

// Java program to demonstrate the 
// working of nested-if statement
import java.util.*;

class Geeks {
    public static void main(String args[])
    {
        int i = 10;

        if (i == 10 || i < 15) {
          
            // First if statement
            if (i < 15)
                System.out.println("i is smaller than 15");

            // Nested - if statement
            // Will only be executed if statement above
            // it is true
            if (i < 12)
                System.out.println(
                    "i is smaller than 12 too");
        }
        else {
            System.out.println("i is greater than 15");
        }
    }
}

i is smaller than 15
i is smaller than 12 too

4. Java if-else-if ladder

Here, a user can decide among multiple options.The if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that ‘if’ is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed. There can be as many as ‘else if’ blocks associated with one ‘if’ block but only one ‘else’ block is allowed with one ‘if’ block.

Syntax:

if (condition1) {

// code to be executed if condition1 is true

} else if (condition2) {

// code to be executed if condition2 is true

} else {

// code to be executed if all conditions are false

}

if-else-if ladder Execution Flow

The below diagram demonstrates the flow chart of an “if-else-if ladder execution flow” in programming

Example: This example demonstrates an if-else-if ladder to check multiple conditions and execute the corresponding block of code based on the value of I.

// Java program to demonstrate the
//  working of if-else-if ladder
import java.util.*;

class Geeks {
    public static void main(String args[])
    {
        int i = 20;

        if (i == 10)
            System.out.println("i is 10");
        else if (i == 15)
            System.out.println("i is 15");
        else if (i == 20)
            System.out.println("i is 20");
        else
            System.out.println("i is not present");
    }
}

i is 20

5. Java Switch Case

The switch statement is a multiway branch statement. It provides an easy way to dispatch execution to different parts of code based on the value of the expression. 

Syntax: 

switch (expression) {

case value1:

// code to be executed if expression == value1

break;

case value2:

// code to be executed if expression == value2

break;

// more cases…

default:

// code to be executed if no cases match

}

switch Statements Execution Flow

The below diagram demonstrates the flow chart of a “switch Statements execution flow” in programming.

Example: The below Java program demonstrates the use of switch-case statement to evaluate multiple fixed values.

// Java program to demonstrates the
//  working of switch statements
import java.io.*;

class Geeks {
    public static void main(String[] args)
    {
        int num = 20;
        switch (num) {
        case 5:
            System.out.println("It is 5");
            break;
        case 10:
            System.out.println("It is 10");
            break;
        case 15:
            System.out.println("It is 15");
            break;
        case 20:
            System.out.println("It is 20");
            break;
        default:
            System.out.println("Not present");
        }
    }
}

It is 20

• The expression can be of type byte, short, int char, or an enumeration. Beginning with JDK7, the expression can also be of type String.
• Duplicate case values are not allowed.
• The default statement is optional.
• The break statement is used inside the switch to terminate a statement sequence.
• The break statements are necessary without the break keyword, statements in switch blocks fall through.  
• If the break keyword is omitted, execution will continue to the next case.

6. jump Statements

Java supports three jump statements: break, continue and return. These three statements transfer control to another part of the program. 

• Break: In Java, a break is majorly used for: 
  
  • Terminate a sequence in a switch statement (discussed above).
  • To exit a loop.
  • Used as a “civilized” form of goto.
• Continue: Sometimes it is useful to force an early iteration of a loop. That is, you might want to continue running the loop but stop processing the remainder of the code in its body for this particular iteration. This is, in effect, a goto just past the body of the loop, to the loop’s end. The continue statement performs such an action. 

Jump Statements Execution Flow

The below diagram demonstrates the flow chart of a “jump Statements execution flow” in programming.

Example: The below Java Program demonstrates how the continue statement skip the current iteration when a condition is true.

// Java program to demonstrates the use of
// continue in an if statement
import java.util.*;

class Geeks {
    public static void main(String args[])
    {
        for (int i = 0; i < 10; i++) {
          
            // If the number is even
            // skip and continue
            if (i % 2 == 0)
                continue;

            // If number is odd, print it
            System.out.print(i + " ");
        }
    }
}

1 3 5 7 9 

Return Statement

The return statement is used to explicitly return from a method. That is, it causes program control to transfer back to the caller of the method.

Example: The below Java program demonstrates how the return statements stop a method and skips the rest of the code.

// Java program to demonstrate the use of return
import java.util.*;

public class Geeks {
    public static void main(String args[])
    {
        boolean t = true;
        System.out.println("Before the return.");

        if (t)
            return;

        // Compiler will bypass every statement
        // after return
        System.out.println("This won't execute.");
    }
}

Before the return.

Comparison of Decision-Making Statements

if-else vs switch-case

The table below demonstrates the difference between if-else and switch-case.

Best Practices for Decision-Making in Java

• Use switch for multiple exact matches, it improves readability.
• Try avoiding deep nesting.
• Always include default in switch for unexpected cases.
• Prefer if-else for range checks.