Gson processing generic

Parse json. I only like simple things. gson is relatively simple. I have been using it. Today I encountered a problem in processing generics.

The object classes used are as follows:

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Class Option {
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Public String itemValue;
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Public String itemLabel;
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Public Option (String itemValue, String itemLabel ){
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This. itemValue = itemValue;
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This. itemLabel = itemLabel;
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}
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}
(1) convert List to json string

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List <Option> options = new ArrayList <Option> ();
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Options. add (new Option ("1", "male "));
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Options. add (new Option ("2", "female "));
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Gson gson = new Gson ();
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String json = gson. toJson (options, List. class );
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System. out. println (json );

Print out [{"itemValue": "1", "itemLabel": "male" },{ "itemValue": "2", "itemLabel": "female"}]

(2) convert the above string to List

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String json = output above
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Gson gson = new Gson ();
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List <Option> options = gson. fromJson (json, List. class );
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For (Iterator it = options. iterator (); it. hasNext ();){
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Option option = (Option) it. next ();
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System. out. println (option. itemLabel );
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}

The following error is reported:

Exception in thread "main" java. lang. ClassCastException: com. google. gson. internal. StringMap cannot be cast
Option

Change

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Gson gson = new Gson ();
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List <Option> options = gson. fromJson (json, new TypeToken <List <Option> () {}. getType ());
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For (Iterator it = options. iterator (); it. hasNext ();){
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Option option = (Option) it. next ();
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System. out. println (option. itemLabel );
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}
Successful!