Java enum reverse look-up best practice

Question

I saw it suggested on a blog that the following was a reasonable way to do a \"reverse-lookup\" using the getCode(int) in a Java enum:

public en         


        

Answer 1

Here is an Java 8 alternative (with unit test):

// DictionarySupport.java :

import org.apache.commons.collections4.Factory;
import org.apache.commons.collections4.map.LazyMap;

import java.util.HashMap;
import java.util.Map;

public interface DictionarySupport> {

    @SuppressWarnings("unchecked")
    Map,  Map> byCodeMap = LazyMap.lazyMap(new HashMap(), (Factory) HashMap::new);

    @SuppressWarnings("unchecked")
    Map,  Map> byEnumMap = LazyMap.lazyMap(new HashMap(), (Factory) HashMap::new);


    default void init(String code) {
        byCodeMap.get(this.getClass()).put(code, this);
        byEnumMap.get(this.getClass()).put(this, code) ;
    }

    static > T getByCode(Class clazz,  String code) {
        clazz.getEnumConstants();
        return (T) byCodeMap.get(clazz).get(code);
    }

    default > String getCode() {
        return byEnumMap.get(this.getClass()).get(this);
    }
}

// Dictionary 1:
public enum Dictionary1 implements DictionarySupport {

    VALUE1("code1"),
    VALUE2("code2");

    private Dictionary1(String code) {
        init(code);
    }
}

// Dictionary 2:
public enum Dictionary2 implements DictionarySupport {

    VALUE1("code1"),
    VALUE2("code2");

    private Dictionary2(String code) {
        init(code);
    }
}

// DictionarySupportTest.java:     
import org.testng.annotations.Test;
import static org.fest.assertions.api.Assertions.assertThat;

public class DictionarySupportTest {

    @Test
    public void teetSlownikSupport() {

        assertThat(getByCode(Dictionary1.class, "code1")).isEqualTo(Dictionary1.VALUE1);
        assertThat(Dictionary1.VALUE1.getCode()).isEqualTo("code1");

        assertThat(getByCode(Dictionary1.class, "code2")).isEqualTo(Dictionary1.VALUE2);
        assertThat(Dictionary1.VALUE2.getCode()).isEqualTo("code2");


        assertThat(getByCode(Dictionary2.class, "code1")).isEqualTo(Dictionary2.VALUE1);
        assertThat(Dictionary2.VALUE1.getCode()).isEqualTo("code1");

        assertThat(getByCode(Dictionary2.class, "code2")).isEqualTo(Dictionary2.VALUE2);
        assertThat(Dictionary2.VALUE2.getCode()).isEqualTo("code2");

    }
}