Fix a compile-time ambiguity when compiling with JDK7.

Patch by lukas.eder@gmail.com

h2/src/docsrc/html/changelog.html

@@ -46,6 +46,7 @@ Change Log
 </ul><li>Support ALTER TABLE ADD ... AFTER. Patch from Andrew Gaul (argaul at gmail.com). Fixes issue 401.
 </ul><li>Improved OSGi support. H2 now registers itself as a DataSourceFactory service. Fixes issue 365.
 </ul><li>Add a DISK_SPACE_USED system function. Fixes issue 270.
+</ul><li>Fix a compile-time ambiguity when compiling with JDK7.
 </li></ul>
 
 <h2>Version 1.3.170 (2012-11-30)</h2>

h2/src/main/org/h2/store/fs/FilePathMem.java

@@ -295,7 +295,8 @@ class FileMem extends FileBase {
                 return null;
             }
         }
-        FileLock lock = new FileLock(null, position, size, shared) {
+        // Cast null to FileChannel to avoid JDK 1.7 ambiguity
+        FileLock lock = new FileLock((FileChannel) null, position, size, shared) {
 
             @Override
             public boolean isValid() {

h2/src/main/org/h2/store/fs/FilePathZip.java

@@ -317,7 +317,8 @@ class FileZip extends FileBase {
 
     public synchronized FileLock tryLock(long position, long size, boolean shared) throws IOException {
         if (shared) {
-            return new FileLock(null, position, size, shared) {
+        	// Cast null to FileChannel to avoid JDK 1.7 ambiguity
+            return new FileLock((FileChannel) null, position, size, shared) {
 
                 @Override
                 public boolean isValid() {

h2/src/tools/org/h2/dev/fs/FilePathZip2.java

@@ -398,7 +398,8 @@ class FileZip2 extends FileBase {
 
     public synchronized FileLock tryLock(long position, long size, boolean shared) throws IOException {
         if (shared) {
-            return new FileLock(null, position, size, shared) {
+        	// Cast null to FileChannel to avoid JDK 1.7 ambiguity
+            return new FileLock((FileChannel) null, position, size, shared) {
 
                 @Override
                 public boolean isValid() {