Porting Guidance

(work in progress)

There are differences between C# and Java at the language level and there are differences at the framework level.

Language Level Differences

Flexible interfaces and enums.

Java allows classes in interfaces and methods inside of enums. In C#, both these cases are illegal and will lead to compile errors.

/**
 * interface with nested class
 */
public interface Bits
{
    public boolean get(int index);

    public int length();


    public class MatchAllBits: Bits
    {   
        final int len;

        public MatchAllBits(int len) {
            this.len = len;
        }

        @Override
        public boolean get(int index) {
          return true;
        }

        @Override
        public int length() {
          return len;
        }
    }
}


/**
 *
 */
public enum Version {
    
    @Deprecated
    LUCENE_4_10,

    LUCENE_5_0,

    @Deprecated
    LUCENE_CURRENT

    public boolean onOrAfter(Version other) {
        return compareTo(other) >= 0;
    }
  
    public static Version parseLeniently(String version) {
        final String parsedMatchVersion = version
            .toUpperCase(Locale.ROOT)
            .replaceFirst("^(\\d+)\\.(\\d+)$", "LUCENE_$1_$2")
            .replaceFirst("^LUCENE_(\\d)(\\d)$", "LUCENE_$1_$2");
        return Version.valueOf(parsedMatchVersion);
    }
} 

When porting the above code in C#, the methods and classes need to extracted. For example, extract the interface into IBits. Extract the methods from the enum into its own static Util class.

public interface IBits
{
    bool this[int index];

    int Length { get; set; }
}

public class Bits
{
    public class MatchAllBits: Bits
    {   
        final int len;

        public MatchAllBits(int len) {
            this.len = len;
        }

        @Override
        public boolean get(int index) {
          return true;
        }

        @Override
        public int length() {
          return len;
        }
    }
}


public enum Version {
    
    @Deprecated
    LUCENE_4_10,

    LUCENE_5_0,

    @Deprecated
    LUCENE_CURRENT;
} 

public static class VersionUtil
{
    public static boolean OnOrAfter(Version current, Version other) 
    {
        return current.CompareTo(other) >= 0;
    }
  
    public static Version ParseLeniently(String version) 
    {
        throw new NotImplementedException();
    }
}