Difference between String and String[] element

[Dalqin]

I'm having a discrepancy between a String I hard code and a String[] array with which I extract a String element from. I'd like to use the String[] array, which I'm filling by using the String.split() method. The array is filling properly and its elements show to be exactly as they should via debug readouts.

So this is what I'm doing, essentially. Just wanting to use a string representation of my object name to see if that object is present in a list. I'll detail the problem out afterwards.

ArrayList<Fruit> fruitList = new ArrayList<Fruit>();
fruitList.add(new Apple());   //all of these are extensions of the class Fruit
fruitList.add(new Orange());
fruitList.add(new Pear());     

String wholeString = "apple orange pear";
String[] fruits = String[5];   //extra size just to be safe for testing
fruits = wholeString.split(" "); //splits the string up by space characters


String element = fruits[0]   //assigns "apple" to the String element


System.out.println(fruitList.contains(new Fruit(element)));//returns false
System.out.println(fruitList.contains(new Fruit(fruits[0])));//returns false

So neither fruitList.contains(new Fruit(element)) nor fruitList.contains(new Fruit(fruits[0])) returns true, which seems weird to me.

Class Fruit takes a string as a parameter, which is assigned to a String instance variable for use with equals() methods, which are written to compare strings that represent the name of the respective object. My problem shouldn't be a method overwriting error because if I hard code a string in, it works.

These below approaches all work, where as the one listed above does not.

fruitList.contains(new Fruit("apple")); //returns true for me when tried

String temp = "apple";
fruitList.contains(new Fruit(temp)); //also returns true for me when tested

So what gives? I've gotten this to work splendidly when I avoid the String[] array, so my equals() method should be fine when I call contains() on my list. I just don't see the difference between a hard coded String a String pulled from a String[] array that was filled using .split().

Any insight would be wonderful. I've spent enough time toying with this that I've run out of idea's for what's going on. :D Thank you much!

[sunde887]

What happens if you print element?

[Junky]

fruitList.add(new Apple());
// above line stores an Apple object in the List

System.out.println(fruitList.contains(new Fruit(element)));
// above line looks for a Fruit object which holds the String "apple" in the List
// obviously the two things are different

[DarrylBurke]

My problem shouldn't be a method overwriting error because if I hard code a string in, it works.

I don't see any logic at all in that. did you override equals() [and hashCode()] in your Fruit class? I'm betting you didn't.

db

[Dalqin]

"apple" is what prints when I print out element.

I over wrote equals methods and they work, I'm positive on that. I didn't write make my own hashCode method to override the parent ones. I was under the assumption this was only used for hashTables. Does that mean .contains() uses .hashCode()? or is doing both just good practice.

[DarrylBurke]

is doing both just good practice.

Read the contract of equals(...) and hashCode() in the documentation for Object.

Could we see your implementation of Fruit#equals(...)?

db

[Dalqin]

This is what I wrote. I think I said this, but just to cover everything I'll list it out.
Class Fruit has an instance variable - private String name;
The constructor takes in a String as a parameter and sets it to this name variable.

Apple, Orange, and Pear extend Fruit with constructors that just super("apple"), super("orange"), or super("pear") respectively.

Equals method is as follows, written just in my Fruit class for the others to share.

public boolean equals(Object o){
     return this.name.equals(o.toString());
}

[DarrylBurke]

OK so now could we see your toString() method? And why should equals(...) use a return value from toString() in the first place?

db

[Dalqin]

public String toString(){
	return name;
}

equals() needs to take in an object as a parameter in order to override things, right? I'm only going to be passing in strings to do a comparison between string representations of objects and objects themselves. I think casting the equals() object parameter to a String would give errors, and I just hate casting and try to avoid it. So I invoked toString() in the object parameter (which will always be a String if I'm careful) to get the name variable of my Fruit (the one I'm checking the list against) with which to compare to this.name.

It's just weird to me that if I hardcode fruitList.contains(new Fruit("apple")) it works, and trying to use my String[] element (that shows to have "apple" as the element I'm trying to use) doesn't work. but if hashCode rewriting is required whenever an equals rewrite is done, then I'm missing that part. I'm reading about the relationship they share in between posts. :p

[Dalqin]

Built my own hashCode() method and it works. Amazing call. Thank you so much for pointing me in a direction and for everyone taking the time to respond to my post. Very prompt and excellent, thanks again! I've some reading to do it seems. >.>