added some documentation

src/main/java/de/neemann/digital/gui/components/listing/Listing.java

@@ -6,12 +6,21 @@ import java.util.ArrayList;
 import java.util.HashMap;
 
 /**
+ * Represents a ROM listing
+ *
  * @author hneemann
  */
 public class Listing implements javax.swing.ListModel<String> {
     private final ArrayList<String> lines;
     private final HashMap<Integer, Integer> addrMap;
 
+    /**
+     * Creates a new instance.
+     * The given file is read.
+     *
+     * @param filename the filename
+     * @throws IOException IOException
+     */
     public Listing(File filename) throws IOException {
         lines = new ArrayList<String>();
         addrMap = new HashMap<>();
@@ -55,6 +64,12 @@ public class Listing implements javax.swing.ListModel<String> {
     public void removeListDataListener(ListDataListener l) {
     }
 
+    /**
+     * returns the line belonging to the given address
+     *
+     * @param addr the address
+     * @return the line or null if not found.
+     */
     public Integer getLine(int addr) {
         return addrMap.get(addr);
     }

src/main/java/de/neemann/digital/gui/components/listing/ROMListingDialog.java

@@ -10,6 +10,9 @@ import java.io.File;
 import java.io.IOException;
 
 /**
+ * The dialog to show the ROM listing while running.
+ * Used to debug assembler code.
+ *
  * @author hneemann
  */
 public class ROMListingDialog extends JDialog implements Observer {
@@ -19,6 +22,13 @@ public class ROMListingDialog extends JDialog implements Observer {
     private final JList<String> list;
     private int lastAddr = -1;
 
+    /**
+     * Creates a new instance
+     *
+     * @param parent the parent frame
+     * @param rom    the rom element
+     * @throws IOException IOException
+     */
     public ROMListingDialog(JFrame parent, ROM rom) throws IOException {
         super(parent, Lang.get("win_listing"), false);
         this.rom = rom;
@@ -36,6 +46,7 @@ public class ROMListingDialog extends JDialog implements Observer {
         listing = new Listing(filename);
         list = new JList<>(listing);
         list.setFont(new Font("monospaced", Font.PLAIN, 12));
+        list.setVisibleRowCount(30);
 
         rom.getAddrIn().addObserver(this);
         hasChanged();

src/main/java/de/neemann/digital/gui/components/listing/package-info.java

@@ -0,0 +1,6 @@
+/**
+ * Contains the classes to hold and show a ROM-Listing
+ *
+ * @author hneemann
+ */
+package de.neemann.digital.gui.components.listing;