#4 Java Class Viewer - support cp_index as zero

FormatCLASS/src/main/java/org/freeinternals/format/classfile/attribute/AttributeCode.java

@@ -55,6 +55,7 @@
  * </a>
  */
 public class AttributeCode extends AttributeInfo {
+
     public static final String ATTRIBUTE_CODE_NODE = "code";
 
     public transient final u2 max_stack;
@@ -231,14 +232,13 @@ public void generateTreeNode(DefaultMutableTreeNode parentNode, final ClassFile
                         (i + 1) + ". " + attr.getName()
                 ));
                 AttributeInfo.generateTreeNode(treeNodeAttributeItem, attr, classFile);
-                
+
                 treeNodeAttribute.add(treeNodeAttributeItem);
             }
 
             parentNode.add(treeNodeAttribute);
         }
     }
-
 
     private void generateSubnode(final DefaultMutableTreeNode rootNode, final AttributeCode.ExceptionTable et, final ClassFile classFile) {
         if (et == null) {
@@ -262,14 +262,14 @@ private void generateSubnode(final DefaultMutableTreeNode rootNode, final Attrib
                 2,
                 "handler_pc: " + et.handler_pc.value
         )));
-        int catch_type = et.catch_type.value;
+        final int catch_type = et.catch_type.value;
+        String catch_type_desc = (catch_type == 0) ? "" : " - " + classFile.getCPDescription(catch_type);
         rootNode.add(new DefaultMutableTreeNode(new JTreeNodeFileComponent(
                 startPosMoving + 6,
                 2,
-                "catch_type: " + catch_type + " - " + classFile.getCPDescription(catch_type)
+                "catch_type: " + catch_type + catch_type_desc
         )));
     }
-
 
     /**
      * The {@code exception_table} structure in {@code Code} attribute.
@@ -282,6 +282,18 @@ public final class ExceptionTable extends FileComponent {
         public transient final u2 start_pc;
         public transient final u2 end_pc;
         public transient final u2 handler_pc;
+
+        /**
+         * If the value of the catch_type item is nonzero, it must be a valid
+         * index into the constant_pool table. The constant_pool entry at that
+         * index must be a CONSTANT_Class_info structure representing a class of
+         * exceptions that this exception handler is designated to catch. The
+         * exception handler will be called only if the thrown exception is an
+         * instance of the given class or one of its subclasses.
+         *
+         * If the value of the catch_type item is zero, this exception handler
+         * is called for all exceptions.
+         */
         public transient final u2 catch_type;
 
         private ExceptionTable(final PosDataInputStream posDataInputStream) throws IOException {

FormatCLASS/src/main/java/org/freeinternals/format/classfile/attribute/AttributeInnerClasses.java

@@ -112,7 +112,7 @@ public void generateTreeNode(DefaultMutableTreeNode parentNode, final ClassFile
             parentNode.add(treeNodeInnerClass);
         }
     }
-    
+
     private void generateSubnode(final DefaultMutableTreeNode rootNode, final AttributeInnerClasses.Class innerClass, final ClassFile classFile) {
         final int startPosMoving = innerClass.getStartPos();
 
@@ -124,17 +124,19 @@ private void generateSubnode(final DefaultMutableTreeNode rootNode, final Attrib
         )));
 
         cp_index = innerClass.outer_class_info_index.value;
+        final String outer_class_info_index_desc = (cp_index == 0) ? "" : " - " + classFile.getCPDescription(cp_index);
         rootNode.add(new DefaultMutableTreeNode(new JTreeNodeFileComponent(
                 startPosMoving + 2,
                 2,
-                "outer_class_info_index: " + cp_index + " - " + classFile.getCPDescription(cp_index)
+                "outer_class_info_index: " + cp_index + outer_class_info_index_desc
         )));
 
         cp_index = innerClass.inner_name_index.value;
+        final String inner_name_index_desc = (cp_index == 0) ? "" : " - " + classFile.getCPDescription(cp_index);
         rootNode.add(new DefaultMutableTreeNode(new JTreeNodeFileComponent(
                 startPosMoving + 4,
                 2,
-                "inner_name_index: " + cp_index + " - " + classFile.getCPDescription(cp_index)
+                "inner_name_index: " + cp_index + inner_name_index_desc
         )));
 
         rootNode.add(new DefaultMutableTreeNode(new JTreeNodeFileComponent(
@@ -143,7 +145,6 @@ private void generateSubnode(final DefaultMutableTreeNode rootNode, final Attrib
                 "inner_class_access_flags: " + innerClass.inner_class_access_flags.value + " - " + innerClass.getModifiers()
         )));
     }
-
 
     /**
      * The {@code classes} structure in {@code InnerClasses} attribute.
@@ -158,7 +159,29 @@ public final class Class extends FileComponent {
         public static final int LENGTH = 8;
 
         public transient final u2 inner_class_info_index;
+        /**
+         * If C is not a member of a class or an interface - that is, if C is a
+         * top-level class or interface or a local class or an anonymous class -
+         * then the value of the outer_class_info_index item must be zero.
+         *
+         * Otherwise, the value of the outer_class_info_index item must be a
+         * valid index into the constant_pool table, and the entry at that index
+         * must be a CONSTANT_Class_info structure representing the class or
+         * interface of which C is a member. The value of the
+         * outer_class_info_index item must not equal the the value of the
+         * inner_class_info_index item.
+         */
         public transient final u2 outer_class_info_index;
+        /**
+         * If C is anonymous, the value of the inner_name_index item must be
+         * zero.
+         *
+         * Otherwise, the value of the inner_name_index item must be a valid
+         * index into the constant_pool table, and the entry at that index must
+         * be a CONSTANT_Utf8_info structure that represents the original simple
+         * name of C, as given in the source code from which this class file was
+         * compiled.
+         */
         public transient final u2 inner_name_index;
         public transient final u2 inner_class_access_flags;