Adding LinkedHashMap object into ArrayList

Question

Here is my code:

ArrayList<LinkedHashMap<String, String>> lev3 = new ArrayList<LinkedHashMap<String, String>>();
LinkedHashMap<String, String> lev4 = new LinkedHashMap<String, String>();

for (int k = 0; k < 2; k++) {
   lev4.clear();
   lev4.put("item0"+k, "subitem0"+k);
   lev4.put("item1"+k, "subitem1"+k);
   lev4.put("item2"+k, "subitem2"+k);
   lev4.put("item3"+k, "subitem3"+k);
   lev4.put("item4"+k, "subitem4"+k);
   lev3.add(lev4);

   System.out.println(lev4);
   System.out.println(lev3);
   System.out.println();
}

As a result:

{item00=subitem00, item10=subitem10, item20=subitem20, item30=subitem30, item40=subitem40}
[{item00=subitem00, item10=subitem10, item20=subitem20, item30=subitem30, item40=subitem40}]

{item01=subitem01, item11=subitem11, item21=subitem21, item31=subitem31, item41=subitem41}
[{item01=subitem01, item11=subitem11, item21=subitem21, item31=subitem31, item41=subitem41}, {item01=subitem01, item11=subitem11, item21=subitem21, item31=subitem31, item41=subitem41}]

Why the second value replaces the first value and duplicate?

Thanks.

Stephan · Accepted Answer · 2013-12-17 20:39:13Z

3

You should add a new instance of LinkedHashMap at each iteration.

answered Dec 17, 2013 at 20:39

Stephan

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Marko Topolnik · Accepted Answer · 2013-12-17 20:40:06Z

0

This code

for (int k = 0; k < 2; k++) {
   lev4.clear();
   ... put stuff in lev4
   lev3.add(lev4);
}

adds the one and the same map instance two times to the list, clearing it twice as well.

answered Dec 17, 2013 at 20:40

Marko Topolnik

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