Methods and Return Value

Main ideas and concepts

• Methods in Java can take inputs and return results

  • Methods can accept parameters (inputs).
  • A method can return a value called a return value, which the caller can store or use.

• Return values vs. printing

  • Earlier, the example method printed results.
  • With return values, the method does not print; instead it returns the computed value so the caller can use it.

• Return type

  • The method declaration includes a return type (e.g., int), which indicates what type the method returns.
  • If you try to assign a method that returns void to a variable, you get an error.

• Method “box” mental model

  • Inputs (parameters) go into the method.
  • A result (return value) comes out.
  • The caller captures that output, e.g. by assigning it to a variable.

• Method signature

  • A method signature consists of:
    • Method name
    • Parameter list
  • Example concept: square(int x) → name is square, parameters are (int x).

Instructional content / methodology

1) Write a method that returns a value

• Define a method with:
  • A return type (e.g., int)
  • A method name
  • A parameter list
• Inside the method:
  • Compute the result
  • Use a return statement to send the computed value back to the caller

Example pattern shown:

private int sum(int a, int b) {
    int total = a + b;
    return total;
}

2) Call a return-value method and use the result

• Store the return value:
  • int result = sum(2, 5);
• Or print directly:
  • System.out.println(sum(10, 20));
• Or call with variables:
  • int total = sum(x, y);

3) Implement and call smaller examples

Add one

• Define:
  • private int addOne(int x)
• Return:
  • return x + 1;
• Usage:
  • int y = addOne(5); → 6
  • int z = addOne(10); → 11

Double a number

• Define:
  • private int doubleNumber(int x)
• Return:
  • return 2 * x;
• Usage:
  • int doubled = doubleNumber(10); → 20

4) Use parameters and return values within course activities (Scratchpad vs Unit Tests)

Scratchpad file

• Acts like a normal coding area you can run.
• You can:
  • Copy method logic into it (e.g., double number)
  • Call methods from the run method
  • Print results to verify behavior quickly
• The Run button runs the scratchpad, not the unit test file.

Unit test file

• Used for checking correctness against multiple test cases.
• The Check code button runs tests on the method logic you implemented.
• You cannot rely on scratchpad output alone for correctness—unit tests validate logic with varied inputs.

Workflow described

1. Build/test method in Scratchpad
2. Copy logic into the method body in the Unit test file
3. Use Check code to confirm it passes all test cases
4. If tests fail, adjust logic and repeat (possibly going back to Scratchpad)

Speakers / sources featured

• No specific individual speaker is identified in the subtitles (presented as one instructional narrator/teacher).
• Source: The video content itself (Java tutorial on methods and return values); no external documents or named authors are referenced.