[Solved] Java: Sort List on basis of particular index [closed]

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Don’t use getClass().toString() to compare types. Use instanceof and try to group types by common interfaces when possible. For example CharSequence is a common interface for String, StringBuilder, and StringBuffer.

Here is one way. You may want to rework the compare method to compare whatever types you have such as Date or URL or custom objects.

public class CompareEverything {

    public static void sort(List someList, int columnNumber) {
        Collections.sort(someList, new EverythingComparator(columnNumber));
    }

    public static class EverythingComparator implements Comparator<List<?>> {
        private int columnNumber;

        public EverythingComparator(int columnNumber) {
            this.columnNumber = columnNumber;
       }

        @Override
        public int compare(List<?> list1, List<?> list2) {
            Object obj1 = list1.get(columnNumber);
            Object obj2 = list2.get(columnNumber);
            return CompareEverything.compare(obj1, obj2);
       }
    }

    public static int compare(Object obj1, Object obj2) {
        int result = 0;
        if (obj1 == null) {
            result = (obj2 == null) ? 0 : -1;
        }
        else if (obj2 == null) {
            result = 1;
        }
        else if (obj1 instanceof CharSequence && obj2 instanceof CharSequence) {
            // String, StringBuilder, StringBuffer, etc.
            result = obj1.toString().compareTo(obj2.toString());
        }
        else if (obj1 instanceof Number && obj2 instanceof Number) {
            Number num1 = (Number)obj1;
            Number num2 = (Number)obj2;
            // Short, Integer, or Long
            if (isIntegral(obj1.getClass()) && isIntegral(obj2.getClass())) {
                result = Long.compare(num1.longValue(), num2.longValue());
            }
            else { // Float, Double, or any mismatched combo
                result = Double.compare(num1.doubleValue(), num2.doubleValue());
            }
        }
        // add other types...
        else {
            // mismatched types - compare as Strings
            // or maybe throw a RuntimeException?
           result = obj1.toString().compareTo(obj2.toString());
        }
        return result;
    }

    private static boolean isIntegral(Class<?> type) {
        return Short.class.equals(type) || Integer.class.equals(type) || Long.class.equals(type);
    }
}

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solved Java: Sort List> on basis of particular index [closed]