Java Generics Usage for List Type

Question

Is there a way to use Java Generics here so my method could take a List<Double> or List<Pair<Double, Double>>?

private Map<Integer, Double> getValuesMap(int indexBegin, int indexEnd, List<Double> values) {
  Map<Integer, Double> map = new LinkedHashMap<>();

  if (indexBegin <= indexEnd) {
    for (int i = indexBegin; i <= indexEnd; i++) {
      map.put(i, values.get(i));
    }
  } else {
    for (int i = indexBegin; i >= indexEnd; i--) {
      map.put(i, values.get(i));
    }
  }

  return map;
}

How would you like this List<Pair<Double, Double>> to be handled if it was passed as argument? What should be expected result? Should it be Map<Integer, Pair<Double, Double>> OR Map<Integer, Double> (if yes, then which Double value from Pair<Double, Double> should be used here) OR maybe something else? — Pshemo
– Pshemo, Commented Nov 23, 2019 at 18:16

Vikas · Accepted Answer · 2019-11-23 18:22:27Z

6

Add generic to your class and use it as below,

public class Test<T> {
private Map<Integer, T> getValuesMap(int indexBegin, int indexEnd, List<T> values) {
        Map<Integer, T> map = new LinkedHashMap<>();

        if (indexBegin <= indexEnd) {
            for (int i = indexBegin; i <= indexEnd; i++) {
                map.put(i, values.get(i));
            }
        } else {
            for (int i = indexBegin; i >= indexEnd; i--) {
                map.put(i, values.get(i));
            }
        }

        return map;
    }

}

Update: You could also use method generic as,

private <T>  Map<Integer, T> getValuesMap(int indexBegin, int indexEnd, List<T> values)

edited Nov 23, 2019 at 18:22

answered Nov 23, 2019 at 18:15

Vikas

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