src/jdk.scripting.nashorn.shell/share/classes/jdk/nashorn/tools/jjs/HistoryObject.java

*** 24,33 ****
--- 24,36 ----
   */
  
  package jdk.nashorn.tools.jjs;
  
  import java.io.IOException;
+ import java.util.Collections;
+ import java.util.HashSet;
+ import java.util.Set;
  import java.util.function.Function;
  import jdk.internal.jline.console.history.FileHistory;
  import jdk.internal.jline.console.history.History;
  import jdk.nashorn.api.scripting.AbstractJSObject;
  import jdk.nashorn.api.scripting.JSObject;
*** 36,45 ****
--- 39,58 ----
  
  /*
   * A script friendly object that exposes history of commands to scripts.
   */
  final class HistoryObject extends AbstractJSObject {
+     private static final Set<String> props;
+     static {
+         final HashSet<String> s = new HashSet<>();
+         s.add("clear");
+         s.add("forEach");
+         s.add("print");
+         s.add("size");
+         props = Collections.unmodifiableSet(s);
+     }
+ 
      private final FileHistory hist;
  
      HistoryObject(final FileHistory hist) {
          this.hist = hist;
      }
*** 70,79 ****
--- 83,97 ----
      @Override
      public String toString() {
          return "[object history]";
      }
  
+     @Override
+     public Set<String> keySet() {
+         return props;
+     }
+ 
      private void print() {
          for (History.Entry e : hist) {
              System.out.println(e.value());
          }
      }