What Is an Implicit Parameter?

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The implicit parameter in Java is the object that the method belongs to. It's passed by specifying the reference or variable of the object before the name of the method. 

An implicit parameter is opposite to an explicit parameter, which is passed when specifying the parameter in the parenthesis of a method call.

If a parameter isn't explicitly defined, the parameter is considered implicit.

Explicit Method Example

When your program calls a method of an object, it's common to pass a value to the method.

For example, if the object Employee has a method called setJobTitle:

 Employee dave = new Employee();
 dave.setJobTitle("Candlestick Maker"); 

...the String "Candlestick Maker" is an explicit parameter being passed to the setJobTitle method.

Implicit Method Example

However, there is another parameter in the method call that is known as the implicit parameter. The implicit parameter is the object the method belongs to. In the above example, it's dave, the object of type Employee.

Implicit parameters are not defined within a method declaration because they are implied by the class the method is in:

 public class Employee {
 
   public void setJobTitle(String jobTitle)
   {
     this.jobTitle = jobTitle;
   }
 } 

In order to call the setJobTitle method, there must be an object of type Employee.

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Leahy, Paul. "What Is an Implicit Parameter?" ThoughtCo, Apr. 2, 2017, thoughtco.com/implicit-parameter-2034139. Leahy, Paul. (2017, April 2). What Is an Implicit Parameter? Retrieved from https://www.thoughtco.com/implicit-parameter-2034139 Leahy, Paul. "What Is an Implicit Parameter?" ThoughtCo. https://www.thoughtco.com/implicit-parameter-2034139 (accessed September 21, 2017).