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Java Java Objects (Retired) Harnessing the Power of Objects Helper Methods

Shubham Modi
Shubham Modi
5,799 Points

Create a helper method that returns whether or not the GoKart needs to be charged. Make it public and name it isBatteryE

How do I do it??

GoKart.java
public class GoKart {
  public static final int MAX_BARS = 8;
  private String mColor;
  private int mBarsCount;

  public GoKart(String color) {
    mColor = color;
    mBarsCount = 0;
  }

  public Integer isBatteryEmpty( ) {
   return mBarsCount; 
  }

  public String getColor() {
    return mColor;
  }

  public void charge() {
    mBarsCount = MAX_BARS;
  }
}

3 Answers

Hi there,

You're along the right lines.

First, the helper method will return a true or false in answer to the question, "is the battery empty".

To do that, compare mBarsCount to zero like mBarsCount == 0 and return that. We use the double equals to test whether the two things are the same.

So, you want to amend your method to return a boolean not an Integer and then return the above comparison. There's just one line required inside your method; the result of the comparison being returned to the caller.

To summarise: Create a public method that returns a boolean and takes no parameters; then return the comparison between mBarsCount and zero. Job done!

Let me know how you get on.

Steve.

gregory gordon
seal-mask
.a{fill-rule:evenodd;}techdegree
gregory gordon
Full Stack JavaScript Techdegree Student 14,652 Points
public boolean isBatteryEmpty( ) {
      if (mBarsCount <= 0){
        return true; 
      } 
     return false;
}

how does this work why is the return false not in the bracets or need anything else declaired?

Hi Gregory,

Your code looks fine and it should work, yes. It could be more brief, as we'll get to in a minute.

You are testing a binary situation; there are two outcomes - either mBarsCount is less than or equal to zero or it is not. There's no middle ground; no overlap at all. mBarsCount is in one camp or the other.

So, your if statement is checking which camp mBarsCount has put its tent in. If it is zero or less, the value true is returned. At this point, your if statement ends. If the code execution has reached this far, that is because the initial condition was not met. So, mBarsCount is greater than zero - there is no alternative. Had mBarsCount been zero or less, the method would have exited at return true. So, now we've got beyond the if statement, it is safe to just return false as there's no other possible outcome to handle.

Do we need the if statement? No, we don't. We can just return the evaluation of the comparison. That comparison produces the same true or false outcome without needing to stipulate what to return.

  public boolean isBatteryEmpty(){
    return mBarsCount == 0;
  }

You can use less than or equal to, or just ==`` for this - that's a question of how often you test and what values you decrement. Logically, however, your code should not allow a battery to be less than empty. That makes no sense! The above method compares the value ofmBarsCountto zero and returns whether they are equal (true) or not (false```).

I hope that helps,

Steve.

Shubham, Look at the following code with comments:

public class GoKart {
  public static final int MAX_BARS = 8;
  private String mColor;
  private int mBarsCount;

  public GoKart(String color) {
    mColor = color;
    mBarsCount = 0;
  }

// It looks like you are on the right track with this method, but lets add to it bit

   public boolean isBatteryE( ) { // Change name to match requirement (instructions)

      // Check Battery to see if it needs to be charged
      if (mBarsCount <= 0){
        return true; // If mBarsCount is less than or equals 0, 
                           //return boolean "true" - the battery needs to be charged
      } 
     return false;  // If mBarsCount is not less than or equal to 0, 
                          // return boolean 'false' the battery does not need to be charged
  }

  public String getColor() {
    return mColor;
  }

  public void charge() {
    mBarsCount = MAX_BARS;
  }
}

Look at this code and see if it makes sense. Your code doesn't have to be the exact same, just check the logic and syntax

If you have more questions, feel free to reply to request for more information.

Cheers and happy coding,