Sort a Map<String, Object> first on Object.property1 and then for each Object.property1, sort by Object.property2

Question

I have used the below method to Sort a Map first on Object.property1 and then for each Object.property1, sort by Object.property2.

for example,

property1 = TaxIdNumber and
property2 = ProviderName

I was just wondering this can be done in a more shorter and precise manner. Any help or suggestion would be appreciated.

    private List<TestObject> sortByValue(final Map m) {
        List<TestObject> values = new ArrayList<TestObject>();
        values.addAll(m.values());

        // First sort the list by Tax ID.
        Collections.sort(values, new Comparator<TestObject>() {
            public int compare(TestObject r1, TestObject r2) {
                Long taxId1 = (r1 == null ? null : r1.getTaxIdNumber());
                Long taxId2 = (r2 == null ? null : r2.getTaxIdNumber());

                if (taxId1 == null || taxId2 == null) {
                    return 0;
                }

                return taxId1.compareTo(taxId2);
            }
        });

        // Then sort the list by Provider name.
        Collections.sort(values, new Comparator<TestObject>() {
            public int compare(TestObject r1, TestObject r2) {
                String name1 = (r1 == null ? null : r1.getProviderName());
                String name2 = (r2 == null ? null : r2.getProviderName());

                if (name1 == null || name2 == null) {
                    return 0;
                }

                if (r1.getTaxIdNumber() == r2.getTaxIdNumber()) {
                    return name1.compareTo(name2);
                } else {
                    return 0;
                }
            }
        });

        return values;
    }

Answer 1

You only need one comparator. first compare the taxids. If they are unequal return -1 or 1 as appropriate. If they are equals, then compare the provider name.

something like:

Collections.sort(values, new Comparator<TestObject>() {
        public int compare(TestObject r1, TestObject r2) {
            Long taxId1 = (r1 == null ? null : r1.getTaxIdNumber());
            Long taxId2 = (r2 == null ? null : r2.getTaxIdNumber());

            if (taxId1 == null || taxId2 == null) {
                return 0;
            }

            int cmp = taxId1.compareTo(taxId2);

            if (cmp != 0)
                return cmp;

            String name1 = (r1 == null ? null : r1.getProviderName());
            String name2 = (r2 == null ? null : r2.getProviderName());

            if (name1 == null || name2 == null) {
                return 0;
            }

            return name1.compareTo(name2);
        }
    });