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List contents - number of occurrences ?

 
kri shan
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List al = new ArrayList();
al.add("James");
al.add("Bill");
al.add("Joe");
al.add("Bill");
al.add("James");
al.add("Joe");
al.add("James");
al.add("Joe");
al.add("steve");
al.add("Joe");

Which is the best optimized way to get each elements number of occurrences like James occurs 3 times, Joe occurs 4 times, Steve occur 1 time.
 
Henry Wong
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This is a pretty common homework problem... so why don't you tell us what you have done so far? And if still in the design phase, what algorithm you are currently considering?

Henry
 
kri shan
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I am planning to use HashSet for storing unique values. Then i will create duplicate keys in the Map based on one of the previous thread.



Finally planning to check the map values with HashSet unique values for incrementing the counter value.
 
antty ge
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I finish it :


syso Result:
 
kri shan
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'result' HashMap does not contain any elements. How containsKey() works here ?
 
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