Method overloading in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is method overloading in Java?

Method overloading is when a class has multiple methods with the same name but different parameters (different type, number, or order). It helps perform similar tasks in different ways.

beginner

Can method overloading change only the return type of methods?

No. Method overloading requires different parameter lists. Changing only the return type is not enough for overloading.

intermediate

How does Java decide which overloaded method to call?

Java looks at the method name and the arguments you pass. It matches the method with the closest parameter types to your arguments.

beginner

Example: What will this code print?

public class Test {
  void show(int a) { System.out.println("int: " + a); }
  void show(String a) { System.out.println("String: " + a); }
  public static void main(String[] args) {
    Test t = new Test();
    t.show(5);
    t.show("Hi");
  }
}

Output: int: 5 String: Hi Explanation: The show method is called with an int and a String, so Java calls the matching overloaded method each time.

beginner

Why is method overloading useful?

It lets you use the same method name for similar actions but with different inputs. This makes code easier to read and organize.

Which of these is a valid method overloading example?

A void print(int a) and void print(String a)

B int add(int a) and int add(int a)

C void show() and int show()

D void run() and void run()

Only methods with the same name but different parameter lists (like int vs String) are valid overloads.

Can two overloaded methods differ only by return type?

A Yes, always

B Yes, if parameters are the same

C No, never

D Only if methods are static

Overloaded methods must differ in parameters, not just return type.

What happens if no matching overloaded method is found?

A Java calls a random method

B Java throws a compile-time error

C Java calls the first method declared

D Java calls the method with the closest return type

If no method matches the call, Java gives a compile-time error.

Which is NOT a way to overload a method?

A Change number of parameters

B Change parameter types

C Change parameter order

D Change method name

Overloading requires same method name; changing name is not overloading.

Why might a programmer use method overloading?

A To reuse method names for similar tasks

B To confuse other programmers

C To reduce the number of classes

D To avoid writing methods

Overloading helps reuse method names for similar actions with different inputs.

Explain method overloading and how Java chooses which method to call.

Think about how you might have many ways to do similar things but with different inputs.

Give an example of method overloading with at least two methods and explain the output when called.

Use simple types like int and String for easy understanding.

Practice

1.

What is method overloading in Java?

easy

A. Changing the return type of a method only

B. Having multiple classes with the same name

C. Using inheritance to override methods

D. Having multiple methods with the same name but different parameters

Solution

1. Step 1: Understand method naming

   Method overloading means methods share the same name.

2. Step 2: Check parameter differences

   They differ by number or type of parameters, not just return type.

3. Final Answer:

   Having multiple methods with the same name but different parameters -> Option D

4. Quick Check:

   Same name + different parameters = method overloading [OK]

Hint: Same method name, different parameters means overloading [OK]

Common Mistakes:

• Confusing overloading with overriding
• Thinking return type alone overloads method
• Mixing class names with method names

2.

Which of the following is a correct method overloading example in Java?

class Test {
  void show(int a) {}
  void show(int a, int b) {}
  void show(int a) {}
}

easy

A. This code compiles without errors

B. Duplicate method show(int a) causes a compile error

C. Method names must be different to overload

D. Return types must differ for overloading

Solution

1. Step 1: Check method signatures

   Two methods have the same name and same parameter list: show(int a).

2. Step 2: Understand overloading rules

   Overloading requires different parameter lists; duplicate signatures cause errors.

3. Final Answer:

   Duplicate method show(int a) causes a compile error -> Option B

4. Quick Check:

   Same parameters = error, not overloading [OK]

Hint: Parameters must differ; identical signatures cause errors [OK]

Common Mistakes:

• Assuming return type difference overloads method
• Ignoring duplicate parameter lists
• Thinking method names must differ

3.

What is the output of this Java code?

class Demo {
  void print(int a) {
    System.out.println("int: " + a);
  }
  void print(String s) {
    System.out.println("String: " + s);
  }
}
public class Main {
  public static void main(String[] args) {
    Demo d = new Demo();
    d.print(5);
    d.print("hello");
  }
}

medium

A. int: 5\nString: hello

B. String: 5\nint: hello

C. int: 5\nint: hello

D. Compilation error

Solution

1. Step 1: Identify method calls and parameters

   First call passes int 5, second call passes String "hello".

2. Step 2: Match calls to overloaded methods

   print(int) prints "int: 5", print(String) prints "String: hello".

3. Final Answer:

   int: 5 String: hello -> Option A

4. Quick Check:

   Correct method chosen by parameter type [OK]

Hint: Method chosen by argument type matches parameter [OK]

Common Mistakes:

• Mixing output order
• Assuming wrong method called
• Expecting compile error

4.

Find the error in this code snippet:

class Calculator {
  int add(int a, int b) { return a + b; }
  double add(double a, double b) { return a + b; }
  int add(int a, int b, int c) { return a + b + c; }
  int add(int a, int b) { return a - b; }
}

medium

A. Duplicate method add(int a, int b) with different body causes error

B. Overloading requires different method names

C. Return type difference causes error

D. No error, code compiles fine

Solution

1. Step 1: Check method signatures

   Two methods have signature add(int a, int b) but different bodies.

2. Step 2: Understand overloading rules

   Overloading requires unique parameter lists; duplicate signatures cause errors regardless of body.

3. Final Answer:

   Duplicate method add(int a, int b) with different body causes error -> Option A

4. Quick Check:

   Same parameters = duplicate method error [OK]

Hint: Same parameters, different body = error, not overloading [OK]

Common Mistakes:

• Thinking different return types fix duplicates
• Ignoring duplicate parameter lists
• Confusing overloading with overriding

5.

Consider this class:

class Converter {
  int convert(String s) { return Integer.parseInt(s); }
  int convert(int i) { return i * 2; }
  int convert(String s, int base) { return Integer.parseInt(s, base); }
}
public class Main {
  public static void main(String[] args) {
    Converter c = new Converter();
    System.out.println(c.convert("10"));
    System.out.println(c.convert(10));
    System.out.println(c.convert("10", 16));
  }
}

What is the output when this code runs?

hard

A. Runtime error parsing string

B. 10\n20\n10

C. 10\n20\n16

D. Compilation error due to ambiguous methods

Solution

1. Step 1: Analyze each method call

   convert("10") parses string "10" as decimal 10; convert(10) doubles 10 to 20; convert("10", 16) parses hex "10" as decimal 16.

2. Step 2: Determine output values

   Outputs are 10, 20, and 16 respectively.

3. Final Answer:

   10 20 16 -> Option C

4. Quick Check:

   Overloaded methods handle inputs correctly [OK]

Hint: Match method by parameters; parseInt with base converts hex [OK]

Common Mistakes:

• Confusing hex parsing result
• Expecting compile or runtime errors
• Mixing method outputs