262      * no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 263      *
 264      * @return a {@code StackWalker} configured to skip all
 265      * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and
 266      * no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 267      *
 268      */
 269     public static StackWalker getInstance() {
 270         // no permission check needed
 271         return DEFAULT_WALKER;
 272     }
 273 
 274     /**
 275      * Returns a {@code StackWalker} instance with the given option specifying
 276      * the stack frame information it can access.
 277      *
 278      * <p>
 279      * If a security manager is present and the given {@code option} is
 280      * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
 281      * it calls its {@link SecurityManager#checkPermission checkPermission}
 282      * method for {@code StackFramePermission("retainClassReference")}.
 283      *
 284      * @param option {@link Option stack walking option}
 285      *
 286      * @return a {@code StackWalker} configured with the given option
 287      *
 288      * @throws SecurityException if a security manager exists and its
 289      *         {@code checkPermission} method denies access.
 290      */
 291     public static StackWalker getInstance(Option option) {
 292         return getInstance(EnumSet.of(Objects.requireNonNull(option)));
 293     }
 294 
 295     /**
 296      * Returns a {@code StackWalker} instance with the given {@code options} specifying
 297      * the stack frame information it can access.  If the given {@code options}
 298      * is empty, this {@code StackWalker} is configured to skip all
 299      * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
 300      * {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 301      *
 302      * <p>
 303      * If a security manager is present and the given {@code options} contains
 304      * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
 305      * it calls its {@link SecurityManager#checkPermission checkPermission}
 306      * method for {@code StackFramePermission("retainClassReference")}.
 307      *
 308      * @param options {@link Option stack walking option}
 309      *
 310      * @return a {@code StackWalker} configured with the given options
 311      *
 312      * @throws SecurityException if a security manager exists and its
 313      *         {@code checkPermission} method denies access.
 314      */
 315     public static StackWalker getInstance(Set<Option> options) {
 316         if (options.isEmpty()) {
 317             return DEFAULT_WALKER;
 318         }
 319 
 320         EnumSet<Option> optionSet = toEnumSet(options);
 321         checkPermission(optionSet);
 322         return new StackWalker(optionSet);
 323     }
 324 
 325     /**
 326      * Returns a {@code StackWalker} instance with the given {@code options} specifying
 327      * the stack frame information it can access. If the given {@code options}
 328      * is empty, this {@code StackWalker} is configured to skip all
 329      * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
 330      * {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 331      *
 332      * <p>
 333      * If a security manager is present and the given {@code options} contains
 334      * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
 335      * it calls its {@link SecurityManager#checkPermission checkPermission}
 336      * method for {@code StackFramePermission("retainClassReference")}.
 337      *
 338      * <p>
 339      * The {@code estimateDepth} specifies the estimate number of stack frames
 340      * this {@code StackWalker} will traverse that the {@code StackWalker} could
 341      * use as a hint for the buffer size.
 342      *
 343      * @param options {@link Option stack walking options}
 344      * @param estimateDepth Estimate number of stack frames to be traversed.
 345      *
 346      * @return a {@code StackWalker} configured with the given options
 347      *
 348      * @throws IllegalArgumentException if {@code estimateDepth <= 0}
 349      * @throws SecurityException if a security manager exists and its
 350      *         {@code checkPermission} method denies access.
 351      */
 352     public static StackWalker getInstance(Set<Option> options, int estimateDepth) {
 353         if (estimateDepth <= 0) {
 354             throw new IllegalArgumentException("estimateDepth must be > 0");
 355         }
 356         EnumSet<Option> optionSet = toEnumSet(options);

 359     }
 360 
 361     // ----- private constructors ------
 362     private StackWalker(EnumSet<Option> options) {
 363         this(options, 0, null);
 364     }
 365     private StackWalker(EnumSet<Option> options, int estimateDepth) {
 366         this(options, estimateDepth, null);
 367     }
 368     private StackWalker(EnumSet<Option> options, int estimateDepth, ExtendedOption extendedOption) {
 369         this.options = options;
 370         this.estimateDepth = estimateDepth;
 371         this.extendedOption = extendedOption;
 372     }
 373 
 374     private static void checkPermission(Set<Option> options) {
 375         Objects.requireNonNull(options);
 376         SecurityManager sm = System.getSecurityManager();
 377         if (sm != null) {
 378             if (options.contains(Option.RETAIN_CLASS_REFERENCE)) {
 379                 sm.checkPermission(new StackFramePermission("retainClassReference"));
 380             }
 381         }
 382     }
 383 
 384     /*
 385      * Returns a defensive copy
 386      */
 387     private static EnumSet<Option> toEnumSet(Set<Option> options) {
 388         Objects.requireNonNull(options);
 389         if (options.isEmpty()) {
 390             return DEFAULT_EMPTY_OPTION;
 391         } else {
 392             return EnumSet.copyOf(options);
 393         }
 394     }
 395 
 396     /**
 397      * Applies the given function to the stream of {@code StackFrame}s
 398      * for the current thread, traversing from the top frame of the stack,
 399      * which is the method calling this {@code walk} method.

 262      * no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 263      *
 264      * @return a {@code StackWalker} configured to skip all
 265      * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and
 266      * no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 267      *
 268      */
 269     public static StackWalker getInstance() {
 270         // no permission check needed
 271         return DEFAULT_WALKER;
 272     }
 273 
 274     /**
 275      * Returns a {@code StackWalker} instance with the given option specifying
 276      * the stack frame information it can access.
 277      *
 278      * <p>
 279      * If a security manager is present and the given {@code option} is
 280      * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
 281      * it calls its {@link SecurityManager#checkPermission checkPermission}
 282      * method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
 283      *
 284      * @param option {@link Option stack walking option}
 285      *
 286      * @return a {@code StackWalker} configured with the given option
 287      *
 288      * @throws SecurityException if a security manager exists and its
 289      *         {@code checkPermission} method denies access.
 290      */
 291     public static StackWalker getInstance(Option option) {
 292         return getInstance(EnumSet.of(Objects.requireNonNull(option)));
 293     }
 294 
 295     /**
 296      * Returns a {@code StackWalker} instance with the given {@code options} specifying
 297      * the stack frame information it can access.  If the given {@code options}
 298      * is empty, this {@code StackWalker} is configured to skip all
 299      * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
 300      * {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 301      *
 302      * <p>
 303      * If a security manager is present and the given {@code options} contains
 304      * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
 305      * it calls its {@link SecurityManager#checkPermission checkPermission}
 306      * method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
 307      *
 308      * @param options {@link Option stack walking option}
 309      *
 310      * @return a {@code StackWalker} configured with the given options
 311      *
 312      * @throws SecurityException if a security manager exists and its
 313      *         {@code checkPermission} method denies access.
 314      */
 315     public static StackWalker getInstance(Set<Option> options) {
 316         if (options.isEmpty()) {
 317             return DEFAULT_WALKER;
 318         }
 319 
 320         EnumSet<Option> optionSet = toEnumSet(options);
 321         checkPermission(optionSet);
 322         return new StackWalker(optionSet);
 323     }
 324 
 325     /**
 326      * Returns a {@code StackWalker} instance with the given {@code options} specifying
 327      * the stack frame information it can access. If the given {@code options}
 328      * is empty, this {@code StackWalker} is configured to skip all
 329      * {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
 330      * {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
 331      *
 332      * <p>
 333      * If a security manager is present and the given {@code options} contains
 334      * {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
 335      * it calls its {@link SecurityManager#checkPermission checkPermission}
 336      * method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
 337      *
 338      * <p>
 339      * The {@code estimateDepth} specifies the estimate number of stack frames
 340      * this {@code StackWalker} will traverse that the {@code StackWalker} could
 341      * use as a hint for the buffer size.
 342      *
 343      * @param options {@link Option stack walking options}
 344      * @param estimateDepth Estimate number of stack frames to be traversed.
 345      *
 346      * @return a {@code StackWalker} configured with the given options
 347      *
 348      * @throws IllegalArgumentException if {@code estimateDepth <= 0}
 349      * @throws SecurityException if a security manager exists and its
 350      *         {@code checkPermission} method denies access.
 351      */
 352     public static StackWalker getInstance(Set<Option> options, int estimateDepth) {
 353         if (estimateDepth <= 0) {
 354             throw new IllegalArgumentException("estimateDepth must be > 0");
 355         }
 356         EnumSet<Option> optionSet = toEnumSet(options);

 359     }
 360 
 361     // ----- private constructors ------
 362     private StackWalker(EnumSet<Option> options) {
 363         this(options, 0, null);
 364     }
 365     private StackWalker(EnumSet<Option> options, int estimateDepth) {
 366         this(options, estimateDepth, null);
 367     }
 368     private StackWalker(EnumSet<Option> options, int estimateDepth, ExtendedOption extendedOption) {
 369         this.options = options;
 370         this.estimateDepth = estimateDepth;
 371         this.extendedOption = extendedOption;
 372     }
 373 
 374     private static void checkPermission(Set<Option> options) {
 375         Objects.requireNonNull(options);
 376         SecurityManager sm = System.getSecurityManager();
 377         if (sm != null) {
 378             if (options.contains(Option.RETAIN_CLASS_REFERENCE)) {
 379                 sm.checkPermission(new RuntimePermission("getStackWalkerWithClassReference"));
 380             }
 381         }
 382     }
 383 
 384     /*
 385      * Returns a defensive copy
 386      */
 387     private static EnumSet<Option> toEnumSet(Set<Option> options) {
 388         Objects.requireNonNull(options);
 389         if (options.isEmpty()) {
 390             return DEFAULT_EMPTY_OPTION;
 391         } else {
 392             return EnumSet.copyOf(options);
 393         }
 394     }
 395 
 396     /**
 397      * Applies the given function to the stream of {@code StackFrame}s
 398      * for the current thread, traversing from the top frame of the stack,
 399      * which is the method calling this {@code walk} method.