How to create a loop through LinkedHashMap<String,ArrayList<String>>?

Question

Please help me to create a loop through LinkedHashMap<String,ArrayList<String>> h:

if (h.get("key1").size() == 0)
    System.out.println("There is no errors in key1.");
else
    System.out.println("ERROR: there are unexpected errors in key1.");

if (h.get("key2").size() == 0)
    System.out.println("There is no errors in key2.");
else
    System.out.println("ERROR: there are unexpected errors in key2.");

if (h.get("key3").size() == 0)
    System.out.println("There is no errors in key3.");
else
    System.out.println("ERROR: there are unexpected errors in key3.");

if (h.get("key4").size() == 0)
    System.out.println("There is no errors in key4.\n");
else
    System.out.println("ERROR: there are unexpected errors in key4.\n");

Bala R · Accepted Answer · 2011-05-05 18:05:54Z

15

Like this?

for (String key : h.keySet())
{
    System.out.println("Key: " + key);   
    for(String str : h.get(key))
    {
       System.out.println("\t" +str);
    }
}

EDIT:

for (String key : h.keySet())
{
    if(h.get(key).size() == 0)
    {
         System.out.println("There is no errors in " + key) ;
    }
    else
    {
        System.out.println("ERROR: there are unexpected errors in " + key);
    }
}

edited May 5, 2011 at 18:05

answered May 5, 2011 at 17:54

Bala R

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4 Comments

Prostak Over a year ago

Can you add my exact messages into your loop?

Bala R Over a year ago

@Prostak check out my edit. sounds like that's what you want.

edthethird Over a year ago

a little late, but does this return in insertion order or do we have to use an iterator? the javadocs for LinkedHashMap are identical to that of a HashMap

vsocrates Over a year ago

LinkedHashMap guarantees it but not all HashMaps do: stackoverflow.com/questions/2923856/…

anubhava · Accepted Answer · 2011-05-05 18:02:15Z

7

Try this code:

Map<String, ArrayList<String>> a = new LinkedHashMap<String, ArrayList<String>>();
Iterator<Entry<String,ArrayList<String>>> itr = a.entrySet().iterator();
while (itr.hasNext()) {
    Entry<String,ArrayList<String>> entry = itr.next();
    String key = entry.getKey();
    System.out.println("key: " + key);
    List<String> list = entry.getValue();
    System.out.println("value: " + list);
}

answered May 5, 2011 at 18:02

anubhava

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2 Comments

Gopinath Over a year ago

Will this return in the insertion order?

anubhava Over a year ago

Yes it will ensure insertion order since LinkedHashMap is being used here.

Kita · Accepted Answer · 2017-08-12 01:33:22Z

5

Another way in Java8 is with the foreach() method

Map<String, List<String>> test1 = new LinkedHashMap<String, List<String>>();
test1.forEach((key,value) -> {
    System.out.println(key + " -> " + value);
});

edited Aug 12, 2017 at 1:33

Kita

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answered Aug 11, 2017 at 21:16

Roberto Gimenez

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