diff --git a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TarFormat.java b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TarFormat.java
index c552fb184..341247645 100644
--- a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TarFormat.java
+++ b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TarFormat.java
@@ -61,7 +61,7 @@
 /**
  * Unix TAR format (ustar + some PAX extensions).
  */
-public class TarFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
+public final class TarFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
 	private static final List<String> SUFFIXES = Collections
 			.unmodifiableList(Arrays.asList(".tar")); //$NON-NLS-1$
 
@@ -118,4 +118,14 @@ public void putEntry(ArchiveOutputStream out,
 	public Iterable<String> suffixes() {
 		return SUFFIXES;
 	}
+
+	@Override
+	public boolean equals(Object other) {
+		return (other instanceof TarFormat);
+	}
+
+	@Override
+	public int hashCode() {
+		return getClass().hashCode();
+	}
 }
diff --git a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/Tbz2Format.java b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/Tbz2Format.java
index 61aa339b7..65e1e7964 100644
--- a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/Tbz2Format.java
+++ b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/Tbz2Format.java
@@ -57,7 +57,7 @@
 /**
  * bzip2-compressed tarball (tar.bz2) format.
  */
-public class Tbz2Format implements ArchiveCommand.Format<ArchiveOutputStream> {
+public final class Tbz2Format implements ArchiveCommand.Format<ArchiveOutputStream> {
 	private static final List<String> SUFFIXES = Collections
 			.unmodifiableList(Arrays.asList(".tar.bz2", ".tbz", ".tbz2")); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
 
@@ -78,4 +78,14 @@ public void putEntry(ArchiveOutputStream out,
 	public Iterable<String> suffixes() {
 		return SUFFIXES;
 	}
+
+	@Override
+	public boolean equals(Object other) {
+		return (other instanceof Tbz2Format);
+	}
+
+	@Override
+	public int hashCode() {
+		return getClass().hashCode();
+	}
 }
diff --git a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TgzFormat.java b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TgzFormat.java
index 534404fad..e13c88a04 100644
--- a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TgzFormat.java
+++ b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TgzFormat.java
@@ -57,7 +57,7 @@
 /**
  * gzip-compressed tarball (tar.gz) format.
  */
-public class TgzFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
+public final class TgzFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
 	private static final List<String> SUFFIXES = Collections
 			.unmodifiableList(Arrays.asList(".tar.gz", ".tgz")); //$NON-NLS-1$ //$NON-NLS-2$
 
@@ -78,4 +78,14 @@ public void putEntry(ArchiveOutputStream out,
 	public Iterable<String> suffixes() {
 		return SUFFIXES;
 	}
+
+	@Override
+	public boolean equals(Object other) {
+		return (other instanceof TgzFormat);
+	}
+
+	@Override
+	public int hashCode() {
+		return getClass().hashCode();
+	}
 }
diff --git a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TxzFormat.java b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TxzFormat.java
index f0eed00fd..d74ca9ba0 100644
--- a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TxzFormat.java
+++ b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/TxzFormat.java
@@ -57,7 +57,7 @@
 /**
  * Xz-compressed tar (tar.xz) format.
  */
-public class TxzFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
+public final class TxzFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
 	private static final List<String> SUFFIXES = Collections
 			.unmodifiableList(Arrays.asList(".tar.xz", ".txz")); //$NON-NLS-1$ //$NON-NLS-2$
 
@@ -78,4 +78,14 @@ public void putEntry(ArchiveOutputStream out,
 	public Iterable<String> suffixes() {
 		return SUFFIXES;
 	}
+
+	@Override
+	public boolean equals(Object other) {
+		return (other instanceof TxzFormat);
+	}
+
+	@Override
+	public int hashCode() {
+		return getClass().hashCode();
+	}
 }
diff --git a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/ZipFormat.java b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/ZipFormat.java
index a2bfbeeb1..e58c7e910 100644
--- a/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/ZipFormat.java
+++ b/org.eclipse.jgit.archive/src/org/eclipse/jgit/archive/ZipFormat.java
@@ -60,7 +60,7 @@
 /**
  * PKWARE's ZIP format.
  */
-public class ZipFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
+public final class ZipFormat implements ArchiveCommand.Format<ArchiveOutputStream> {
 	private static final List<String> SUFFIXES = Collections
 			.unmodifiableList(Arrays.asList(".zip")); //$NON-NLS-1$
 
@@ -105,4 +105,14 @@ public void putEntry(ArchiveOutputStream out,
 	public Iterable<String> suffixes() {
 		return SUFFIXES;
 	}
+
+	@Override
+	public boolean equals(Object other) {
+		return (other instanceof ZipFormat);
+	}
+
+	@Override
+	public int hashCode() {
+		return getClass().hashCode();
+	}
 }