Use Map interface instead of ConcurrentHashMap class

On Android, the co-variant override of ConcurrentHashMap.keySet()
introduced in Java 8 was undone. [1] If compiled Java code calls that
co-variant override directly, one gets a NoSuchMethodError exception
at run-time on Android.

Making the code call that method via Map.keySet() side-steps this
problem.

This is similar to bug 496262, where the same problem cropped up when
compiling with Java 8 against a Java 7 target, but here we cannot use
bootclasspath. We build against Java 8, not against the Android version
of it.

Recent Android versions should have some bytecode "magic" that adds the
co-variant override in bytecode (see the commit referenced in [1]), but
on older Android version this problem may still occur. (Or perhaps the
"magic" is ineffective...) There are two pull requests on Github for
this problem, both from 2020, [2][3] while the Android commit [1] is
from March 2018. Apparently people still occasionally run into this
problem in the wild.

[1] 0e8b937ded/ojluni/src/main/java/java/util/concurrent/ConcurrentHashMap.java (1244)
[2] https://github.com/eclipse/jgit/pull/104
[3] https://github.com/eclipse/jgit/pull/100

Change-Id: I7c07e0cc59871cb7fe60795e22867827fa9c2458
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

org.eclipse.jgit.junit.http/src/org/eclipse/jgit/junit/http/AppServer.java

 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
 
 import org.eclipse.jetty.http.HttpVersion;
 import org.eclipse.jetty.security.AbstractLoginService;
 	static class TestMappedLoginService extends AbstractLoginService {
 		private String role;
 
-		protected final ConcurrentMap<String, UserPrincipal> users = new ConcurrentHashMap<>();
+		protected final Map<String, UserPrincipal> users = new ConcurrentHashMap<>();
 
 		TestMappedLoginService(String role) {
 			this.role = role;

org.eclipse.jgit/src/org/eclipse/jgit/api/ArchiveCommand.java

 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
 
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.api.errors.JGitInternalException;
 	 * Available archival formats (corresponding to values for
 	 * the --format= option)
 	 */
-	private static final ConcurrentMap<String, FormatEntry> formats =
+	private static final Map<String, FormatEntry> formats =
 			new ConcurrentHashMap<>();
 
 	/**
 	 * @param newValue value to be associated with the key (null to remove).
 	 * @return true if the value was replaced
 	 */
-	private static <K, V> boolean replace(ConcurrentMap<K, V> map,
+	private static <K, V> boolean replace(Map<K, V> map,
 			K key, V oldValue, V newValue) {
 		if (oldValue == null && newValue == null) // Nothing to do.
 			return true;

org.eclipse.jgit/src/org/eclipse/jgit/attributes/FilterCommandRegistry.java

 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
  * @since 4.6
  */
 public class FilterCommandRegistry {
-	private static ConcurrentHashMap<String, FilterCommandFactory> filterCommandRegistry = new ConcurrentHashMap<>();
+	private static Map<String, FilterCommandFactory> filterCommandRegistry = new ConcurrentHashMap<>();
 
 	/**
 	 * Register a {@link org.eclipse.jgit.attributes.FilterCommandFactory}

org.eclipse.jgit/src/org/eclipse/jgit/events/ListenerList.java

 package org.eclipse.jgit.events;
 
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 
 /**
  * Manages a thread-safe list of {@link org.eclipse.jgit.events.RepositoryListener}s.
  */
 public class ListenerList {
-	private final ConcurrentMap<Class<? extends RepositoryListener>, CopyOnWriteArrayList<ListenerHandle>> lists = new ConcurrentHashMap<>();
+	private final Map<Class<? extends RepositoryListener>, CopyOnWriteArrayList<ListenerHandle>> lists = new ConcurrentHashMap<>();
 
 	/**
 	 * Register a {@link org.eclipse.jgit.events.WorkingTreeModifiedListener}.

org.eclipse.jgit/src/org/eclipse/jgit/lib/RepositoryCache.java

 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 		cache.configureEviction(repositoryCacheConfig);
 	}
 
-	private final ConcurrentHashMap<Key, Repository> cacheMap;
+	private final Map<Key, Repository> cacheMap;
 
 	private final Lock[] openLocks;
 

org.eclipse.jgit/src/org/eclipse/jgit/nls/NLS.java

 package org.eclipse.jgit.nls;
 
 import java.util.Locale;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
 import org.eclipse.jgit.errors.TranslationBundleLoadingException;
 	}
 
 	private final Locale locale;
-	private final ConcurrentHashMap<Class, TranslationBundle> map = new ConcurrentHashMap<>();
+
+	private final Map<Class, TranslationBundle> map = new ConcurrentHashMap<>();
 
 	private NLS(Locale locale) {
 		this.locale = locale;