Add new abstract builder that collects the attributes of the compound keep expressions

src/main/java/org/rosi_project/model_sync/model_join/representation/grammar/CompoundKeepBuilder.java

+package org.rosi_project.model_sync.model_join.representation.grammar;
+
+import java.util.List;
+
+import javax.annotation.Nonnull;
+
+import org.rosi_project.model_sync.model_join.representation.core.ClassResource;
+
+public abstract class CompoundKeepBuilder {
+
+	protected ClassResource target;
+	@Nonnull
+	protected List<KeepExpression> keeps;
+	
+	/**
+     * Specifies the name of the class that should be generated for the subtype instances.
+     */
+    @Nonnull
+    public CompoundKeepBuilder as(@Nonnull ClassResource target) {
+      this.target = target;
+      return this;
+    }
+
+    /**
+     * Adds a {@link KeepExpression keep statement} for the subtype-class. The described attribute
+     * will be initialized for each instantiated subtype element.
+     */
+    @Nonnull
+    public CompoundKeepBuilder keep(@Nonnull KeepExpression keep) {
+      this.keeps.add(keep);
+      return this;
+    }
+    
+    @Nonnull
+    public abstract KeepExpression buildExpression();
+
+}

src/main/java/org/rosi_project/model_sync/model_join/representation/grammar/KeepReferenceExpression.java

@@ -53,14 +53,10 @@ public class KeepReferenceExpression extends CompoundKeepExpression {
    *
    * @author Rico Bergmann
    */
-  public static class KeepReferenceBuilder {
+  public static class KeepReferenceBuilder extends CompoundKeepBuilder {
 
     private ReferenceDirection referenceDirection;
     private AttributePath attribute;
-    private ClassResource target;
-
-    @Nonnull
-    private List<KeepExpression> keeps;
 
     /**
      * Default constructor.
@@ -89,24 +85,6 @@ public class KeepReferenceExpression extends CompoundKeepExpression {
       return this;
     }
 
-    /**
-     * Specifies the name of the attribute in the target join.
-     */
-    @Nonnull
-    public KeepReferenceBuilder as(@Nonnull ClassResource target) {
-      this.target = target;
-      return this;
-    }
-
-    /**
-     * Adds an attribute to the view for the referenced instances.
-     */
-    @Nonnull
-    public KeepReferenceBuilder keep(@Nonnull KeepExpression keepExpression) {
-      this.keeps.add(keepExpression);
-      return this;
-    }
-
     /**
      * Finishes the construction process.
      */

src/main/java/org/rosi_project/model_sync/model_join/representation/grammar/KeepSubTypeExpression.java

@@ -25,11 +25,9 @@ public class KeepSubTypeExpression extends CompoundKeepExpression {
    *
    * @author Rico Bergmann
    */
-  public static class KeepSubTypeBuilder {
+  public static class KeepSubTypeBuilder extends CompoundKeepBuilder {
 
     private ClassResource typeToKeep;
-    private ClassResource target;
-    private List<KeepExpression> keeps;
 
     /**
      * Default constructor.
@@ -47,25 +45,6 @@ public class KeepSubTypeExpression extends CompoundKeepExpression {
       return this;
     }    
 
-    /**
-     * Specifies the name of the class that should be generated for the subtype instances.
-     */
-    @Nonnull
-    public KeepSubTypeBuilder as(@Nonnull ClassResource target) {
-      this.target = target;
-      return this;
-    }
-
-    /**
-     * Adds a {@link KeepExpression keep statement} for the subtype-class. The described attribute
-     * will be initialized for each instantiated subtype element.
-     */
-    @Nonnull
-    public KeepSubTypeBuilder keep(@Nonnull KeepExpression keep) {
-      this.keeps.add(keep);
-      return this;
-    }
-
     /**
      * Finishes the construction process.
      */

src/main/java/org/rosi_project/model_sync/model_join/representation/grammar/KeepSuperTypeExpression.java

@@ -24,11 +24,9 @@ public class KeepSuperTypeExpression extends CompoundKeepExpression {
    *
    * @author Rico Bergmann
    */
-  public static class KeepSuperTypeBuilder {
+  public static class KeepSuperTypeBuilder extends CompoundKeepBuilder {
 
     private ClassResource typeToKeep;
-    private ClassResource target;
-    private List<KeepExpression> keeps;
 
     /**
      * Default constructor.
@@ -46,25 +44,6 @@ public class KeepSuperTypeExpression extends CompoundKeepExpression {
       return this;
     }
 
-    /**
-     * Specifies the name of the class that should be generated for the subtype instances.
-     */
-    @Nonnull
-    public KeepSuperTypeBuilder as(@Nonnull ClassResource target) {
-      this.target = target;
-      return this;
-    }
-
-    /**
-     * Adds a {@link KeepExpression keep statement} for the subtype-class. The described attribute
-     * will be initialized for each instantiated subtype element.
-     */
-    @Nonnull
-    public KeepSuperTypeBuilder keep(@Nonnull KeepExpression keep) {
-      this.keeps.add(keep);
-      return this;
-    }
-
     /**
      * Finishes the construction process.
      */