retrieve array from hashmap

Question

I'm trying to create a hashmap which has a String key and stores an Integer array. While using hashmap.get() , I want to retrieve the stored array. I've used to following code:

HashMap hm = new HashMap();
String[] arr=new String[]{"-1","-1","-1","-1"};
hm.put("A", arr);
hm.put("B", arr);
hm.put("C", arr);
hm.put("E", arr);
Set set = hm.entrySet();
Iterator i = set.iterator();
while(i.hasNext()) 
{
    Map.Entry me = (Map.Entry)i.next();
    System.out.print(me.getKey() + ": ");
    System.out.println(me.getValue());
}

The output i'm getting is:

D: [Ljava.lang.String;@88d00c6
E: [Ljava.lang.String;@88d00c6
A: [Ljava.lang.String;@88d00c6
B: [Ljava.lang.String;@88d00c6
C: [Ljava.lang.String;@88d00c6

Can anyone please help!!

Check out the `Object#toString()` method. – Sotirios Delimanolis Dec 22 '13 at 18:03 — Sotirios Delimanolis, Dec 22 '13 at 18:03

Suresh Atta · Answer 1 · 2013-12-23T13:23:14.153

3

 System.out.println(me.getValue());

That each value is an Array. When you print, by default Object#toString() method calls and result in that hex string.

Try to use the util method from Arrays class, to print array.

System.out.println(Arrays.toString(me.getValue()));

edited Dec 23 '13 at 13:23

answered Dec 22 '13 at 18:06

Suresh Atta

120,458
37
198
307

I actually have to print the data stored in the hashmap... the data that i retrieve from the map..Arrays.toString() does not work for objects... me.getValue() is an object – Mohit Dec 23 '13 at 13:22
@Mohit When I said array that mean me.getValue() :) – Suresh Atta Dec 23 '13 at 13:23

score 2 · Answer 2 · answered Dec 22 '13 at 18:05

2

use Arrays.toString(me.getValue()); instead, default implementation of array Object's toString() doesn't return in pretty format

answered Dec 22 '13 at 18:05

jmj

237,923
42
401
438

Arrays.toString() does not work for objects... me.getValue() is an object – Mohit Dec 23 '13 at 13:22
@Mohit you could use generics so Arrays.toString() will recieve String[] – jmj Dec 23 '13 at 16:18

Flight Odyssey · Accepted Answer · 2013-12-23T15:09:00.120

1

System.out.println uses the default toString method for arrays, which is ugly (some people claim it is the memory address of the array in the virtual machine). Instead, use a utility function or print the array's contents manually.

while(i.hasNext()) 
{
    Map.Entry me = (Map.Entry)i.next();
    System.out.print(me.getKey() + ": ");
    String[] value = (String[])me.getValue();
    for(String str:value)
    {
        System.out.println(str+"\t");
    }
    System.out.println();
}

edited Dec 23 '13 at 15:09

answered Dec 22 '13 at 18:10

Flight Odyssey

2,267
18
25

at String[] value = me.getValue(); it gives an error "cannot convert objects into strings" – Mohit Dec 23 '13 at 13:18
@Mohit: Thanks for pointing that out, fixed now. I just forgot to [cast](http://stackoverflow.com/questions/5289393/casting-variables-in-java). – Flight Odyssey Dec 23 '13 at 15:12

retrieve array from hashmap

3 Answers3