如何访问Java对象的某些部分？

Question

I'm almost positive this question has been asked before, as I'm sure I'm not the first person to have this problem, but I don't know the right search words to get my answer, so if you could point me in the right direction, I'd really appreciate it.

I have an Object in a Java class, that when I mouse over, says:

variableName = Object[6]
  >[0] = "words in here"
  >[1] = "a few more words"
  >[2] = float
  >[3] = float
  >[4] = integer
  >[5] = integer

I want to print out "words in here" and get the value of the integer in [5]. How do I do this? I've tried a couple of things like

String whatsNeeded = variableName[0];
String whatToGet = variableName.toString();

But neither of those get what I want. In fact, variableName[0] gives me an error, and variableName.toString() prints [Ljava.lang.Object;@ blahblah

Any tips on how to get the fields I want? Thanks!!

Answer 1

String whatsNeeded = variableName[0];

Gives you an error because you have an Object[] type, so variableName[0] has type Object , not String . You must downcast it: String whatsNeeded = (String)variableName[0] .

Regarding variableName.toString() , toString on an array data type doesn't work as you intend and just prints the reference in memory. You should use Arrays.toString(variableName) to get a proper printed value.

Looking at your comment it looks like you can't access items of variableName through [] operator. This happens because you probably assigned it to an Object type variable, eg:

Object[] array = new Object[6];
Object object = array;

array[0] // valid
object[0] // invalid, it is an array at runtime but not at compile time

If that's the case you must first cast it to an array:

Object asArray = (Object[])variableName;
String whatsNeeded = (String)asArray[0];

Answer 2

尝试投射，例如：

 String tmp=(String)varName[0];

Answer 3

When you do this:

variableName.toString()

you are invoking the toString method so you need to know how it's working or you can override the method.

Now, if you want to print one element of your array, in this case the first element, you need to know the type of the object, if your program is dynamic, then you need a set of methods or only "if" sentences to verify each element of your array and finally you must do a casting on the object, for example:

if (variableName[0] instanceof String) {
((String)variableName[0]).toString();
}

I hope this information helps you.

Good luck.