How to readout Array from hash map?

Question

I have a problem in understanding how to readout a array that I put into the hash map. (By the way I need to put in different data types into the hash map, single values and also arrays, thatsway I use the generic "Object" type).

Example Code:

HashMap map = new HashMap();

map.put("two", new int[]{1,2});

int[] myArray = new int[2]:

myArray = (int[])map.get("two");

System.out.println("Array value "+myArray[0]);

System.out.println("Array value "+myArray[1]);

I get an error during runtime...

I hope somebody can give me a hint. I can't find my mistake.

Thanks a lot. Steffen

As an aside you might want to use an ArrayList as opposed to an []. You can use Generics etc then. — Martijn Verburg
– Martijn Verburg, Commented Dec 13, 2010 at 12:09
The line int[] myArray = new int[2]; is unnecessary. You are re-assigning the myArray variable using myArray = (int[])map.get("two");. — Koekiebox
– Koekiebox, Commented Dec 13, 2010 at 12:46

Boris Pavlović · Accepted Answer · 2010-12-13 12:02:58Z

1

Problem is within this line:

int[] myArray = new int[2]:

change it to

int[] myArray = new int[2];

Other then that there are no problems with the snippet.

answered Dec 13, 2010 at 12:02

Boris Pavlović

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Comments

Jon Skeet · Accepted Answer · 2010-12-13 12:03:31Z

0

That code should work fine, with the exception of this line:

int[] myArray = new int[2]:

which uses a colon instead of a semi-colon, and pointlessly creates a new array. Given that you say you get an error at runtime, I suspect this isn't the problem - but it's hard to say, given that you haven't said what the error actually is.

I'd also suggest using generics rather than the raw type, even if the value type is just Object. Here's a short but complete program showing it working:

import java.util.*;

public class Test {
  public static void main(String[] args) {
    Map<String, Object> map = new HashMap<String, Object>();
    map.put("two", new int[] { 1, 2 });
    int[] myArray = (int[]) map.get("two");
    System.out.println("Array value " + myArray[0]);
    System.out.println("Array value " + myArray[1]);
  }
}

Output:

Array value 1
Array value 2

Given that that code works, please post a short but complete program which fails - or at least tell us what error you're actually getting.

answered Dec 13, 2010 at 12:03

Jon Skeet

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2 Comments

Jon Skeet Over a year ago

@org.life.java: Yes... I suspect the code that was posted isn't exactly the code that was failing.

Steffen Over a year ago

Dear all, you are correct. The code is working. Unfortunately I was to fast posting my question. The bug is somwhere else, I need to investigate. Thank you, and sorry again. Steffen

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