list - Alphabetizing in Java- error and warnings? -
i'm trying create program alphabetizes list, using collections.sort method , java.util.list, error is: 1 error , 15 warnings found:
error: java.util.list abstract; cannot instantiated -------------- ** warnings ** -------------- warning: unchecked call add(e) member of raw type java.util.list warning: unchecked method invocation: method sort in class java.util.collections applied given types required: java.util.list<t> found: java.util.list
my code:
public static void preset(){ list words= new list(); words.add("apple"); words.add("country"); words.add("couch"); words.add("shoe"); words.add("school"); words.add("computer"); words.add("yesterday"); words.add("wowza"); words.add("happy"); words.add("tomorrow"); words.add("today"); words.add("research"); words.add("project"); collections.sort(words); } //end of method preset
just error said, list
abstract, need concrete implementation. in case posted, arraylist
do.
also note using list
raw type; don't (unless using version before java 5). parameterize type parameter (here, string
).
yet also: don't change declaration of words
arraylist
: list
enough (normally), , left unchanged, gain ability change implementation later on.
in conclusion:
list<string> words= new arraylist<string>();
or if using java 7:
list<string> words= new arraylist<>();
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