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Java Java Objects (Retired) Harnessing the Power of Objects Method Signatures

Kshatriiya .
Kshatriiya .
1,464 Points
Posted by Kshatriiya .
Kshatriiya .
1,464 Points

Confused by Two load methods

Hello in the video there were two different load methods:

public  void load() {
load(MAX_PEZ);
}

public void load (int pezAmount) {
mPezCount += pezAmount;
}

1) My first question is, what is the purpose of the first load method then now that second method actually let you input the amount to be loaded? (is it to act as a default function?)

is it to keep this method alive? : 

if (dispenser.isEmpty()) {
System.out.println("Loading...");
dispenser.load(); }

2) It is my understanding that second method functions independent of the second load method but not the other way round, please clarify if this is the case.

Thank you very much in advance.

Alex Garcia
Alex Garcia
6,374 Points
  1. To make it simple; the first load method he created would always load 12. So whether the pez count was 4 or 6 it would load up to the total amount of 12. The second method allows you to load up to the number inputted. So if you had 4 and wanted to only load 3 it would come out to 7 instead of loading all 12.
  2. The first method is dependent on the second method because it is going to use the lines of code to add a total of 12 which is the assigned value of MAX_PEZ. The second method is independent of the first.

1 Answer

jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

The second load() method overloads the first. To overload means to write a method with the same name but a different method signature (number and type of parameters).

A really good example of overloading are the 8 println() methods. There is one for ints, one for doubles, one for Strings, etc. The overloaded methods make it possible for you to print ints, doubles, Strings, etc.

In this case one load() method, when called, assigns mPezCount the max pezAmount.

   public void load() {
      load(MAX_PEZ);
   }

If you only have this load method you wouldn't be able to refill a dispenser until it was completely empty.

The other assigns a variable amount: the amount passed in as a parameter:

public void load (int pezAmount) {
mPezCount += pezAmount;
}

This method allows you to top up a dispenser, adding just the amount you want to, or the amount needed to fill the dispenser.

These two load() methods do not act independently. The first calls the second. Before it was modified it was independent:

   public void load() {
    mPezCount = MAX_PEZ;
   }

But now, with the modification, it calls load(int pezAmount) with the max amount.

Why do this? Doing it this way conforms to the DRY principle. You do not want to reproduce in load() any of the code in load(int pezAmount).

There really is no such thing as a default function, unless by "default" you mean a no-parameter function.

Here's an excerpt from the Java API re println. All these methods are in the same class (PrintStream). Each of the 9 after println() overload println():

void    println()
Terminates the current line by writing the line separator string.
void    println(boolean x)
Prints a boolean and then terminate the line.
void    println(char x)
Prints a character and then terminate the line.
void    println(char[] x)
Prints an array of characters and then terminate the line.
void    println(double x)
Prints a double and then terminate the line.
void    println(float x)
Prints a float and then terminate the line.
void    println(int x)
Prints an integer and then terminate the line.
void    println(long x)
Prints a long and then terminate the line.
void    println(Object x)
Prints an Object and then terminate the line.
void    println(String x)
Prints a String and then terminate the line.