Add private inteface methods parsing in JavaParser (#14643)

Author: rochala

compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala

@@ -594,7 +594,7 @@ object JavaParsers {
           val vparams = formalParams()
           if (!isVoid) rtpt = optArrayBrackets(rtpt)
           optThrows()
-          val bodyOk = !inInterface || mods.isOneOf(Flags.DefaultMethod | Flags.JavaStatic)
+          val bodyOk = !inInterface || mods.isOneOf(Flags.DefaultMethod | Flags.JavaStatic | Flags.Private)
           val body =
             if (bodyOk && in.token == LBRACE)
               methodBody()

tests/pos/i12956.java

@@ -0,0 +1,3 @@
+interface Foo {
+  private void bar() {}
+}