Convert java version 1.8 to 1.7 compatible

Question

Just to be clear I am not a java developer.

I have java code written for version 1.8. However, the java.util.function is not available in version 1.7 hence I am not able to compile the code. How can I compile\\convert the code to make it compatible to version 1.7 compiler?

below is the code

import java.util.*;
import java.util.function.Predicate;     
public List<PersonSearchResult> searchPersonListAsPerson( Person bean, short minScore, int maxResults, String cvwName, Person.PersonSource[] sources,  Person.PersonAttribute[] attributes) throws MasterDataServiceException {
            logServiceBegin(log, "searchPersonListAsPerson");
            PersonMapper mapper = new PersonMapper();
            List<PersonSearchResult> searchResults = searchForRecordList( mapper, bean, PersonEntityId.getStaticEntType(), minScore, maxResults, cvwName, sources, attributes);        
            if(searchResults != null && searchResults.size() > 1) {
                PersonPredicate pPredicate = new PersonPredicate();
                //TODO: Where to get the srccode as per below??
                //pPredicate.setSrcCodeToTest("CRDSCNCTP");
                //searchResults = searchResults.stream().filter(pPredicate).collect(Collectors.toList());
                //TODO: what if there is no result with that src code searchResults will become empty
                if(searchResults != null && searchResults.size() > 1){
                    Collections.sort(searchResults, new Comparator<PersonSearchResult>(){
                        public int compare(PersonSearchResult a, PersonSearchResult b) {
                            if(isNullOrEmpty(a.getPerson().getPerAttributesList()) && isNullOrEmpty(b.getPerson().getPerAttributesList())){
                                return 0;
                            }else if(isNullOrEmpty(b.getPerson().getPerAttributesList())){
                                return -1;
                            }else if(isNullOrEmpty(a.getPerson().getPerAttributesList())){
                                return 1;
                            }else{
                                int comparison = a.getPerson().getPerAttributesList().get(0).getStatus().compareToIgnoreCase(b.getPerson().getPerAttributesList().get(0).getStatus());
                                return comparison == 0 ? b.getPerson().getPerAttributesList().get(0).getUpdateDate().compareTo(a.getPerson().getPerAttributesList().get(0).getUpdateDate()) : comparison;
                            }
                        }
                    });
                }
            }
            logServiceEnd(log, "searchPersonListAsPerson");
            cleanUserCredentials();
            return searchResults;
        }

        private boolean isNullOrEmpty(List<Memperson> list){
            return list == null || list.isEmpty();
        }


class PersonPredicate implements Predicate<PersonSearchResult>{
        String srcCodeToTest;
        public boolean test(PersonSearchResult person) {                
            return srcCodeToTest.equalsIgnoreCase(person.getPerson().getPersonId().getSrcCode());
        }
        public void setSrcCodeToTest(String srcCodeToTest){
            this.srcCodeToTest = srcCodeToTest;
        }

Answer 1

The code can be written using java 8 streams as:

return searchResults.stream()
        .filter((PersonSearchResult p) -> "CRDSCNCTP".equalsIgnoreCase(p.getPerson().getPersonId().getSrcCode()))
        .sorted(new PersonComparator())
        .collect(Collectors.toList());

If you want to rewrite the java 8 expression in java 7 compatible form / syntax you can do it the following way:

 PersonPredicate predicate = new PersonPredicate("CRDSCNCTP");
 List<PersonSearchResult> searchResults = ...;
 List<PersonSearchResult> filteredResult = filter(searchResult, predicate);
 List<PersonSearchResult> result = Collections.sort(filteredResult , new PersonComparator()); 

where filter is something like

 private static List<PersonSearchResult> filter(List<PersonSearchResult> sourceList, Predicate<PersonSearchResult> predicate) {
     List<PersonSearchResult> result = new ArrayList<PersonSearchResult>();
     if (sourceList != null) {
        for (PersonSearchResult p: sourceList ) { 
            if ( p != null  && predicate.test(p) ){
              result.add(p);  
        }
     }
     return result;        
 }

we still need to define the Predicate Interface. By having a look at the Java 8 API and the knowledge that we only need the test method we can define it as:

interface Predicate<T> {
  public boolean test(T t); 
}

the PersonComparator is that what you've defined as anoymous inner class.

Answer 2

Okay, you asked for code, so here you go:

import java.util.*;
import com.google.common.base.Predicate;     
import com.google.common.collect.Lists;
import com.google.common.collect.Iterables;

public class YourClassName {
public List<PersonSearchResult> searchPersonListAsPerson( Person bean, short minScore, int maxResults, String cvwName, Person.PersonSource[] sources,  Person.PersonAttribute[] attributes) throws MasterDataServiceException {
            logServiceBegin(log, "searchPersonListAsPerson");
            PersonMapper mapper = new PersonMapper();
            List<PersonSearchResult> searchResults = searchForRecordList( mapper, bean, PersonEntityId.getStaticEntType(), minScore, maxResults, cvwName, sources, attributes);        
            if(searchResults != null && searchResults.size() > 1) {
            List<PersonSearchResult> results = Lists.new ArrayList()
                PersonPredicate pPredicate = new PersonPredicate();
                pPredicate.setSrcCodeToTest("CRDSCNCTP");
                Iterable<PersonSearchResult> result = Iterables.filter(searchResults, pPredicate);
                List result = Lists.newArrayList(result);
                if(result.size() > 0){
                    Collections.sort(result, new Comparator<PersonSearchResult>(){
                        public int compare(PersonSearchResult a, PersonSearchResult b) {
                            if(isNullOrEmpty(a.getPerson().getPerAttributesList()) && isNullOrEmpty(b.getPerson().getPerAttributesList())){
                                return 0;
                            }else if(isNullOrEmpty(b.getPerson().getPerAttributesList())){
                                return -1;
                            }else if(isNullOrEmpty(a.getPerson().getPerAttributesList())){
                                return 1;
                            }else{
                                int comparison = a.getPerson().getPerAttributesList().get(0).getStatus().compareToIgnoreCase(b.getPerson().getPerAttributesList().get(0).getStatus());
                                return comparison == 0 ? b.getPerson().getPerAttributesList().get(0).getUpdateDate().compareTo(a.getPerson().getPerAttributesList().get(0).getUpdateDate()) : comparison;
                            }
                        }
                    });
                }
            }
            logServiceEnd(log, "searchPersonListAsPerson");
            cleanUserCredentials();
            return searchResults;
        }

        private boolean isNullOrEmpty(List<Memperson> list){
            return list == null || list.isEmpty();
        }

}
class PersonPredicate implements Predicate<PersonSearchResult>{
        String srcCodeToTest;
        public boolean apply(PersonSearchResult person) {                
            return srcCodeToTest.equalsIgnoreCase(person.getPerson().getPersonId().getSrcCode());
        }
        public void setSrcCodeToTest(String srcCodeToTest){
            this.srcCodeToTest = srcCodeToTest;
        }
}

Please add guava library to your project as well. If there are some errors, do tell. I did it in a hurry.

Answer 3

The easiest way of doing it without adding any external dependencies is to just filter the collection yourself:

//TODO: Where to get the srccode as per below??
srcCode = "CRDSCNCTP";
searchResults = new LinkedList<>(searchResults);
Iterator<PersonSearchResult> it = searchResults.iterator();
while(it.hasNext()) {
    PersonSearchResult p = it.next();
    String pSrcCode = p.getPerson().getPersonId().getSrcCode();
    if(!srcCode.equalsIgnoreCase(pSrcCode)) {
        it.remove();
    }
}
if(searchResults != null && searchResults.size() > 1){
    ...