Primitive data types in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of integer division and casting

What is the output of this Java code snippet?

Java

public class Main {
    public static void main(String[] args) {
        int a = 7;
        int b = 2;
        double c = a / b;
        System.out.println(c);
    }
}

A 3.5

B 3.6

C 3

D 3.0

💡 Hint

Remember that dividing two integers results in an integer before assignment.

In Java, dividing two integers performs integer division, so 7 / 2 equals 3. Assigning this to a double variable converts 3 to 3.0.

❓ Predict Output

intermediate

Output of char arithmetic

What is the output of this Java code?

Java

public class Main {
    public static void main(String[] args) {
        char ch = 'A';
        int result = ch + 2;
        System.out.println(result);
    }
}

A 65

B C

C 67

D 2

💡 Hint

Remember that char is treated as a number in arithmetic.

The char 'A' has ASCII value 65. Adding 2 results in 67, which is printed as an int.

❓ Predict Output

advanced

Output of boolean logic with primitives

What is the output of this Java program?

Java

public class Main {
    public static void main(String[] args) {
        boolean a = true;
        boolean b = false;
        boolean c = a && !b || b;
        System.out.println(c);
    }
}

A true

B false

C null

D Compilation error

💡 Hint

Evaluate the boolean expression step by step.

a is true, b is false, so !b is true. Then a && !b is true && true = true. true || false is true.

❓ Predict Output

advanced

Output of float precision and casting

What is the output of this Java code?

Java

public class Main {
    public static void main(String[] args) {
        float f = 1.23456789f;
        double d = f;
        System.out.println(d);
    }
}

A 1.234567

B 1.2345679

C 1.23456789

D 1.234568

💡 Hint

Float has less precision than double.

The float value loses precision beyond 7 digits. When assigned to double, it keeps the float precision, printing approximately 1.2345679.

🧠 Conceptual

expert

Memory size of primitive types

Which primitive data type in Java uses the most memory?

A double

B int

C long

D float

💡 Hint

Think about the number of bytes each type uses.

double uses 8 bytes (64 bits), which is more than int (4 bytes) and float (4 bytes). Although long and double both use 8 bytes, double stores floating-point numbers, so it is considered the largest in terms of precision.

Practice

1. Which of the following is NOT a primitive data type in Java?

easy

A. char

B. boolean

C. int

D. String

Solution

1. Step 1: Recall Java primitive types

   Java primitive types include int, boolean, char, byte, short, long, float, and double.

2. Step 2: Identify non-primitive type

   String is a class in Java, not a primitive type.

3. Final Answer:

   String -> Option D

4. Quick Check:

   Primitive types exclude classes like String [OK]

Hint: Remember primitives are simple types, not objects like String [OK]

Common Mistakes:

• Confusing String as primitive
• Thinking boolean is not primitive
• Mixing wrapper classes with primitives

2. Which of the following is the correct way to declare a variable of type byte in Java?

easy

A. byte b = 127;

B. byte b = 128;

C. byte b = 'a';

D. byte b = 128L;

Solution

1. Step 1: Understand byte range

   byte stores values from -128 to 127 inclusive.

2. Step 2: Check each option

   byte b = 128; uses 128 which is out of range; byte b = 127; uses 127 which is valid; byte b = 'a'; assigns a char which is not directly compatible; byte b = 128L; uses long literal 128L which is invalid for byte.

3. Final Answer:

   byte b = 127; -> Option A

4. Quick Check:

   byte max value = 127 [OK]

Hint: byte max is 127, so use values within -128 to 127 [OK]

Common Mistakes:

• Assigning values outside byte range
• Using char or long literals directly
• Not knowing byte limits

3. What is the output of the following Java code?

int x = 5;
float y = 2.0f;
System.out.println(x + y);

medium

A. 7.0

B. 7.0f

C. 7

D. 7.0d

Solution

1. Step 1: Understand type promotion in expression

   int x is promoted to float when added to float y.

2. Step 2: Calculate the sum and output type

   5 + 2.0f = 7.0 (float), but println prints float as decimal number without suffix.

3. Final Answer:

   7.0 -> Option A

4. Quick Check:

   int + float = float output 7.0 [OK]

Hint: int + float results in float decimal output [OK]

Common Mistakes:

• Expecting integer output
• Confusing float suffix in output
• Ignoring type promotion rules

4. Identify the error in the following Java code snippet:

char c = 'AB';

medium

A. char cannot be assigned a value directly

B. Missing semicolon at end

C. char can only hold a single character

D. char must be initialized with a number

Solution

1. Step 1: Check char assignment rules

   char stores a single 16-bit Unicode character, so it must be assigned a single character in single quotes.

2. Step 2: Analyze the given code

   'AB' is two characters, which is invalid for char type.

3. Final Answer:

   char can only hold a single character -> Option C

4. Quick Check:

   char = single character only [OK]

Hint: char holds exactly one character in single quotes [OK]

Common Mistakes:

• Assigning multiple characters to char
• Confusing char with String
• Forgetting single quotes for char

5. You want to store a large whole number that is bigger than int can hold. Which primitive type should you use in Java?

hard

A. short

B. long

C. float

D. double

Solution

1. Step 1: Recall int and long ranges

   int holds up to about 2 billion (2^31-1), long holds much larger values (2^63-1).

2. Step 2: Choose type for large whole number

   long is the correct primitive type for large integers beyond int range; float and double are for decimals, short is smaller than int.

3. Final Answer:

   long -> Option B

4. Quick Check:

   Use long for large integers beyond int [OK]

Hint: Use long for big whole numbers beyond int range [OK]

Common Mistakes:

• Using float/double for whole numbers
• Choosing short which is smaller
• Not knowing long size