If Else Decision Making

Decision making is the heart of programming. In Java, the if-else statement lets a program take different paths based on conditions. Combined with logical operators it becomes a powerful tool for solving real-world problems such as login checks, eligibility tests, grade calculations and more.

• if (condition) { /* statements */ }
• if-else: if (cond) { … } else { … }
• else-if: use multiple else if blocks before a final else.
• Conditions return a boolean — true or false.

Let's start with a hands-on example. The program below shows the core idea behind If Else in just a few lines of Java. Read it line by line and observe how Java executes each statement in order.

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

        if (age >= 18)
        {
            System.out.println("You can vote");
        }
        else
        {
            System.out.println("Not eligible");
        }
    }
}

The following examples progress from simple to more practical patterns. Try each in your IDE, change the inputs and observe the output. This is the fastest way to internalize the concept.

class Main
{
    public static void main(String args[])
    {
        int a = 25, b = 14;

        if (a > b)
            System.out.println(a + " is larger");
        else
            System.out.println(b + " is larger");
    }
}

class Main
{
    public static void main(String args[])
    {
        int n = 7;

        if (n % 2 == 0)
            System.out.println(n + " is even");
        else
            System.out.println(n + " is odd");
    }
}

class Main
{
    public static void main(String args[])
    {
        int marks = 76;

        if (marks >= 90)       System.out.println("A+");
        else if (marks >= 80)  System.out.println("A");
        else if (marks >= 70)  System.out.println("B");
        else if (marks >= 60)  System.out.println("C");
        else                   System.out.println("F");
    }
}

class Main
{
    public static void main(String args[])
    {
        int a = 10, b = 25, c = 18;

        if (a > b)
        {
            if (a > c)
                System.out.println("a is largest");
            else
                System.out.println("c is largest");
        }
        else
        {
            if (b > c)
                System.out.println("b is largest");
            else
                System.out.println("c is largest");
        }
    }
}

class Main
{
    public static void main(String args[])
    {
        int n = 12;

        String type = (n % 2 == 0) ? "Even" : "Odd";

        System.out.println(type);
    }
}

• Curly braces { } are optional for a single statement but recommended for readability.
• Always use == for comparison and = for assignment — a common beginner bug.
• Compare strings with equals(), not ==.
• Use the ternary operator only for short, simple conditions.
• Indent your code consistently — it makes nested ifs far easier to read.

Reading is not enough — practice solidifies knowledge. Try every question below in your own editor before peeking at any solution.

• Q1. Check whether a number entered by user is positive, negative or zero.
• Q2. Find the largest of three numbers using nested if.
• Q3. Check if a year is a leap year.
• Q4. Determine if a triangle is equilateral, isosceles or scalene.
• Q5. Print whether a character is a vowel or consonant.

These are the most common questions asked in Java interviews on this topic. Memorize the concept, not just the answer — interviewers often follow up with edge cases.

Even experienced developers slip on the same pitfalls. Watch out for these classic mistakes while working with If Else in Java:

• Forgetting the semicolon ; at the end of statements while using If Else.
• Mixing up similar method names — read Java docs before using new APIs related to If Else.
• Ignoring compiler warnings — they often hint at bugs that will appear later in production.
• Hard-coding values that should come from configuration files or environment variables.
• Not handling edge cases: empty inputs, very large inputs, negative numbers and null references.
• Skipping unit tests — small tests prevent big regressions, especially around control flow.