The Java Language Specification, Third Edition

More documents

Recommendations

Info

14.21 Unreachable Statements BLOCKS AND STATEMENTS 402 DISCUSSION The problem with mandating a backtrace is that an exception can be created at one point in the program and thrown at a later one. It is prohibitively expensive to store a stack trace in an exception unless it is actually thrown (in which case the trace may be generated while unwinding the stack). Hence we do not mandate a back trace in every exception. 14.21 Unreachable Statements That looks like a path. Is that the way to reach the top from here? It is a compile-time error if a statement cannot be executed because it is unreachable. Every Java compiler must carry out the conservative flow analysis specified here to make sure all statements are reachable. This section is devoted to a precise explanation of the word “reachable.” The idea is that there must be some possible execution path from the beginning of the constructor, method, instance initializer or static initializer that contains the statement to the statement itself. The analysis takes into account the structure of statements. Except for the special treatment of while, do, and for statements whose condition expression has the constant value true, the values of expressions are not taken into account in the flow analysis. For example, a Java compiler will accept the code: { int n = 5; while (n > 7) k = 2; } even though the value of n is known at compile time and in principle it can be known at compile time that the assignment to k can never be executed. A Java compiler must operate according to the rules laid out in this section. The rules in this section define two technical terms: • whether a statement is reachable • whether a statement can complete normally DRAFT The definitions here allow a statement to complete normally only if it is reachable.
BLOCKS AND STATEMENTS Unreachable Statements 14.21 To shorten the description of the rules, the customary abbreviation “iff” is used to mean “if and only if.” The rules are as follows: • The block that is the body of a constructor, method, instance initializer or static initializer is reachable. • An empty block that is not a switch block can complete normally iff it is reachable. A nonempty block that is not a switch block can complete normally iff the last statement in it can complete normally. The first statement in a nonempty block that is not a switch block is reachable iff the block is reachable. Every other statement S in a nonempty block that is not a switch block is reachable iff the statement preceding S can complete normally. • A local class declaration statement can complete normally iff it is reachable. • A local variable declaration statement can complete normally iff it is reachable. • An empty statement can complete normally iff it is reachable. • A labeled statement can complete normally if at least one of the following is true: ◆ The contained statement can complete normally. ◆ There is a reachable break statement that exits the labeled statement. The contained statement is reachable iff the labeled statement is reachable. • An expression statement can complete normally iff it is reachable. • The if statement, whether or not it has an else part, is handled in an unusual manner. For this reason, it is discussed separately at the end of this section. • An assert statement can complete normally iff it is reachable. • A switch statement can complete normally iff at least one of the following is true: DRAFT ◆ The last statement in the switch block can complete normally. ◆ The switch block is empty or contains only switch labels. ◆ There is at least one switch label after the last switch block statement group. ◆ The switch block does not contain a default label. ◆ There is a reachable break statement that exits the switch statement. • A switch block is reachable iff its switch statement is reachable. 403
Page 1 and 2:
The Java Language Specification Th
Page 3 and 4:
The Java Language Specification Th
Page 5 and 6:
Copyright © 1996-2005 Sun Microsys
Page 7 and 8:
“When I use a word,” Humpty Dum
Page 9 and 10:
Preface XXIII Preface to the Second
Page 11 and 12:
5.4 String Conversion 101 5.5 Casti
Page 13 and 14:
8.2.1.3 Inheritance with private 19
Page 15 and 16:
10 Arrays 287 10.1 Array Types 288
Page 17 and 18:
14 Blocks and Statements 359 14.1 N
Page 19 and 20:
15.12.4.4 Locate Method to Invoke 4
Page 21 and 22:
17.4.2 Actions 558 17.4.3 Programs
Page 23 and 24:
Preface THE Java programming langua
Page 25 and 26:
PREFACE was invaluable to us during
Page 27 and 28:
Preface to the Second Edition ... t
Page 29 and 30:
PREFACE TO THE SECOND EDITION Trici
Page 31 and 32:
Preface to the Third Edition This e
Page 33 and 34:
PREFACE TO THE THIRD EDITION Joe Da
Page 35 and 36:
1.0 CHAPTER1 Introduction If I have
Page 37 and 38:
INTRODUCTION Introduction 1 declare
Page 39 and 40:
INTRODUCTION Example Programs 1.1 B
Page 41 and 42:
INTRODUCTION References 1.4 Goldber
Page 43 and 44:
CHAPTER2 Grammars Grammar, which kn
Page 45 and 46:
GRAMMARS Grammar Notation 2.4 actua
Page 47 and 48:
CHAPTER3 Lexical Structure Lexicogr
Page 49 and 50:
LEXICAL STRUCTURE Unicode Escapes 3
Page 51 and 52:
LEXICAL STRUCTURE Input Elements an
Page 53 and 54:
LEXICAL STRUCTURE Identifiers 3.8 E
Page 55 and 56:
LEXICAL STRUCTURE Literals 3.10 3.9
Page 57 and 58:
LEXICAL STRUCTURE Integer Literals
Page 59 and 60:
LEXICAL STRUCTURE Floating-Point Li
Page 61 and 62:
LEXICAL STRUCTURE Character Literal
Page 63 and 64:
LEXICAL STRUCTURE String Literals 3
Page 65 and 66:
LEXICAL STRUCTURE Operators 3.12 3.
Page 67 and 68:
CHAPTER4 Types, Values, and Variabl
Page 69 and 70:
TYPES, VALUES, AND VARIABLES Integr
Page 71 and 72:
TYPES, VALUES, AND VARIABLES Floati
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
TYPES, VALUES, AND VARIABLES The bo
Page 79 and 80:
TYPES, VALUES, AND VARIABLES Object
Page 81 and 82:
TYPES, VALUES, AND VARIABLES The Cl
Page 83 and 84:
TYPES, VALUES, AND VARIABLES Type V
Page 85 and 86:
TYPES, VALUES, AND VARIABLES Parame
Page 87 and 88:
TYPES, VALUES, AND VARIABLES Type A
Page 89 and 90:
TYPES, VALUES, AND VARIABLES Member
Page 91 and 92:
TYPES, VALUES, AND VARIABLES Raw Ty
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
TYPES, VALUES, AND VARIABLES Subtyp
Page 99 and 100:
TYPES, VALUES, AND VARIABLES Where
Page 101 and 102:
TYPES, VALUES, AND VARIABLES Variab
Page 103 and 104:
TYPES, VALUES, AND VARIABLES Kinds
Page 105 and 106:
TYPES, VALUES, AND VARIABLES Initia
Page 107 and 108:
TYPES, VALUES, AND VARIABLES Types,
Page 109 and 110:
TYPES, VALUES, AND VARIABLES Types,
Page 111 and 112:
CHAPTER5 Conversions and Promotions
Page 113 and 114:
CONVERSIONS AND PROMOTIONS Conversi
Page 115 and 116:
CONVERSIONS AND PROMOTIONS Widening
Page 117 and 118:
CONVERSIONS AND PROMOTIONS Narrowin
Page 119 and 120:
CONVERSIONS AND PROMOTIONS Narrowin
Page 121 and 122:
CONVERSIONS AND PROMOTIONS Boxing C
Page 123 and 124:
CONVERSIONS AND PROMOTIONS Capture
Page 125 and 126:
CONVERSIONS AND PROMOTIONS Capture
Page 127 and 128:
CONVERSIONS AND PROMOTIONS Assignme
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
CONVERSIONS AND PROMOTIONS Method I
Page 135 and 136:
CONVERSIONS AND PROMOTIONS Casting
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
CONVERSIONS AND PROMOTIONS Unary Nu
Page 145 and 146:
CONVERSIONS AND PROMOTIONS Binary N
Page 147 and 148:
CHAPTER6 Names The Tao that can be
Page 149 and 150:
NAMES Names and Identifiers 6.2 ❖
Page 151 and 152:
NAMES Scope of a Declaration 6.3 in
Page 153 and 154:
NAMES Shadowing Declarations 6.3.1
Page 155 and 156:
NAMES Shadowing Declarations 6.3.1
Page 157 and 158:
NAMES The Members of a Class Type 6
Page 159 and 160:
NAMES The Members of an Array Type
Page 161 and 162:
NAMES Syntactic Classification of a
Page 163 and 164:
NAMES Reclassification of Contextua
Page 165 and 166:
NAMES Meaning of Package Names 6.5.
Page 167 and 168:
NAMES Meaning of Type Names 6.5.5 a
Page 169 and 170:
NAMES Meaning of Expression Names 6
Page 171 and 172:
NAMES Meaning of Method Names 6.5.7
Page 173 and 174:
NAMES Details on protected Access 6
Page 175 and 176:
NAMES Example: Access to public and
Page 177 and 178:
NAMES Example: protected Fields, Me
Page 179 and 180:
NAMES Fully Qualified Names and Can
Page 181 and 182:
NAMES Class and Interface Type Name
Page 183 and 184:
NAMES Method Names 6.8.4 DISCUSSION
Page 185 and 186:
NAMES Local Variable and Parameter
Page 187 and 188:
CHAPTER7 Packages Good things come
Page 189 and 190:
PACKAGES Storing Packages in a File
Page 191 and 192:
PACKAGES Compilation Units 7.3 7.2.
Page 193 and 194:
PACKAGES Unnamed Packages 7.4.2 on
Page 195 and 196:
PACKAGES Single-Type-Import Declara
Page 197 and 198:
PACKAGES Type-Import-on-Demand Decl
Page 199 and 200:
PACKAGES A Strange Example 7.5.6 7.
Page 201 and 202:
PACKAGES Top Level Type Declaration
Page 203 and 204:
PACKAGES Unique Package Names 7.7 t
Page 205 and 206:
PACKAGES Unique Package Names 7.7 o
Page 207 and 208:
CHAPTER8 Classes Origins: A Short E
Page 209 and 210:
CLASSES Class Modifiers 8.1.1 8.1 C
Page 211 and 212:
CLASSES Class Modifiers 8.1.1 class
Page 213 and 214:
CLASSES Generic Classes and Type Pa
Page 215 and 216:
CLASSES Inner Classes and Enclosing
Page 217 and 218:
CLASSES Inner Classes and Enclosing
Page 219 and 220:
CLASSES Superclasses and Subclasses
Page 221 and 222:
CLASSES Superinterfaces 8.1.5 resul
Page 223 and 224:
CLASSES Class Body and Member Decla
Page 225 and 226:
CLASSES Class Members 8.2 Construct
Page 227 and 228:
CLASSES Examples of Inheritance 8.2
Page 229 and 230:
CLASSES Examples of Inheritance 8.2
Page 231 and 232:
CLASSES Field Modifiers 8.3.1 If a
Page 233 and 234:
CLASSES Field Modifiers 8.3.1 of ac
Page 235 and 236:
CLASSES Initialization of Fields 8.
Page 237 and 238:
CLASSES Initialization of Fields 8.
Page 239 and 240:
CLASSES Examples of Field Declarati
Page 241 and 242:
CLASSES Examples of Field Declarati
Page 243 and 244:
CLASSES Method Declarations 8.4 fie
Page 245 and 246:
CLASSES Formal Parameters 8.4.1 of
Page 247 and 248:
CLASSES Method Signature 8.4.2 Two
Page 249 and 250:
CLASSES Method Modifiers 8.4.3 an i
Page 251 and 252:
CLASSES Method Modifiers 8.4.3 resp
Page 253 and 254:
CLASSES Method Modifiers 8.4.3 Thes
Page 255 and 256:
CLASSES Method Throws 8.4.6 • If
Page 257 and 258:
CLASSES Method Body 8.4.7 Object do
Page 259 and 260:
CLASSES Inheritance, Overriding, an
Page 261 and 262:
CLASSES Inheritance, Overriding, an
Page 263 and 264:
CLASSES Overloading 8.4.9 DISCUSSIO
Page 265 and 266:
CLASSES Examples of Method Declarat
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
CLASSES Member Type Declarations 8.
Page 273 and 274:
CLASSES Static Initializers 8.7 aga
Page 275 and 276:
CLASSES Constructor Modifiers 8.8.3
Page 277 and 278:
CLASSES Constructor Body 8.8.7 clas
Page 279 and 280:
CLASSES Constructor Body 8.8.7 •
Page 281 and 282:
CLASSES Default Constructor 8.8.9 8
Page 283 and 284:
CLASSES Enums 8.9 8.9 Enums An enum
Page 285 and 286:
CLASSES Enums 8.9 DISCUSSION This i
Page 287 and 288:
CLASSES Enums 8.9 Note that the exa
Page 289 and 290:
CLASSES Enums 8.9 DIME: 10¢ SILVER
Page 291 and 292:
CLASSES Enums 8.9 public static voi
Page 293 and 294:
CHAPTER9 Interfaces My apple trees
Page 295 and 296:
INTERFACES Superinterfaces and Subi
Page 297 and 298:
INTERFACES Interface Members 9.2 9.
Page 299 and 300:
INTERFACES Examples of Field Declar
Page 301 and 302:
INTERFACES Inheritance and Overridi
Page 303 and 304:
INTERFACES Examples of Abstract Met
Page 305 and 306:
INTERFACES Annotation Types 9.6 DIS
Page 307 and 308:
Page 309 and 310:
Page 311 and 312:
INTERFACES Predefined Annotation Ty
Page 313 and 314:
INTERFACES Predefined Annotation Ty
Page 315 and 316:
INTERFACES Annotations 9.7 • The
Page 317 and 318:
INTERFACES Annotations 9.7 TypeName
Page 319 and 320:
INTERFACES Annotations 9.7 The seco
Page 321 and 322:
CHAPTER10 Arrays Even Solomon in al
Page 323 and 324:
ARRAYS Array Access 10.4 Here are s
Page 325 and 326:
ARRAYS Array Initializers 10.6 Arra
Page 327 and 328:
ARRAYS Class Objects for Arrays 10.
Page 329 and 330:
ARRAYS Array Store Exception 10.10
Page 331 and 332:
CHAPTER11 Exceptions If anything ca
Page 333 and 334:
EXCEPTIONS Exception Analysis of Ex
Page 335 and 336:
EXCEPTIONS Why Runtime Exceptions a
Page 337 and 338:
EXCEPTIONS Handling Asynchronous Ex
Page 339 and 340:
EXCEPTIONS An Example of Exceptions
Page 341 and 342:
EXCEPTIONS Virtual Machine Errors 1
Page 343 and 344:
CHAPTER12 Execution We must all han
Page 345 and 346:
EXECUTION Initialize Test: Execute
Page 347 and 348:
EXECUTION The Loading Process 12.2.
Page 349 and 350:
EXECUTION Resolution of Symbolic Re
Page 351 and 352:
EXECUTION When Initialization Occur
Page 353 and 354:
EXECUTION Detailed Initialization P
Page 355 and 356:
EXECUTION Initialization: Implicati
Page 357 and 358:
EXECUTION Creation of New Class Ins
Page 359 and 360:
EXECUTION Finalization of Class Ins
Page 361 and 362:
EXECUTION Implementing Finalization
Page 363 and 364:
EXECUTION Finalizer Invocations are
Page 365 and 366:
EXECUTION Program Exit 12.8 ers. A
Page 367 and 368:
CHAPTER13 Binary Compatibility Desp
Page 369 and 370:
BINARY COMPATIBILITY The Form of a
Page 371 and 372:
BINARY COMPATIBILITY The Form of a
Page 373 and 374:
BINARY COMPATIBILITY What Binary Co
Page 375 and 376:
BINARY COMPATIBILITY Superclasses a
Page 377 and 378:
BINARY COMPATIBILITY Class Body and
Page 379 and 380:
BINARY COMPATIBILITY Field Declarat
Page 381 and 382:
BINARY COMPATIBILITY final Fields a
Page 383 and 384:
BINARY COMPATIBILITY static Fields
Page 385 and 386: BINARY COMPATIBILITY Method and Con
Page 387 and 388: BINARY COMPATIBILITY final Methods
Page 389 and 390: BINARY COMPATIBILITY Method and Con
Page 391 and 392: BINARY COMPATIBILITY Interface Form
Page 393 and 394: CHAPTER14 Blocks and Statements He
Page 395 and 396: BLOCKS AND STATEMENTS Local Class D
Page 397 and 398: BLOCKS AND STATEMENTS Local Variabl
Page 399 and 400: BLOCKS AND STATEMENTS Scope of Loca
Page 401 and 402: BLOCKS AND STATEMENTS Execution of
Page 403 and 404: BLOCKS AND STATEMENTS Statements 14
Page 405 and 406: BLOCKS AND STATEMENTS Expression St
Page 407 and 408: BLOCKS AND STATEMENTS The assert St
Page 409 and 410: BLOCKS AND STATEMENTS The assert St
Page 411 and 412: BLOCKS AND STATEMENTS The switch St
Page 413 and 414: BLOCKS AND STATEMENTS The switch St
Page 415 and 416: BLOCKS AND STATEMENTS Abrupt Comple
Page 417 and 418: BLOCKS AND STATEMENTS Example of do
Page 419 and 420: BLOCKS AND STATEMENTS The basic for
Page 421 and 422: BLOCKS AND STATEMENTS The enhanced
Page 423 and 424: BLOCKS AND STATEMENTS The break Sta
Page 425 and 426: BLOCKS AND STATEMENTS The continue
Page 427 and 428: BLOCKS AND STATEMENTS The throw Sta
Page 429 and 430: BLOCKS AND STATEMENTS The synchroni
Page 431 and 432: BLOCKS AND STATEMENTS The try state
Page 433 and 434: BLOCKS AND STATEMENTS Execution of
Page 435: BLOCKS AND STATEMENTS Execution of
Page 439 and 440: BLOCKS AND STATEMENTS Unreachable S
Page 441 and 442: BLOCKS AND STATEMENTS Unreachable S
Page 443 and 444: CHAPTER15 Expressions When you can
Page 445 and 446: EXPRESSIONS Expressions and Run-Tim
Page 447 and 448: EXPRESSIONS Normal and Abrupt Compl
Page 449 and 450: EXPRESSIONS Evaluate Left-Hand Oper
Page 451 and 452: EXPRESSIONS Evaluation Respects Par
Page 453 and 454: EXPRESSIONS Evaluation Order for Ot
Page 455 and 456: EXPRESSIONS this 15.8.3 ing-point l
Page 457 and 458: EXPRESSIONS Class Instance Creation
Page 459 and 460: EXPRESSIONS Determining Enclosing I
Page 461 and 462: EXPRESSIONS Choosing the Constructo
Page 463 and 464: EXPRESSIONS Anonymous Class Declara
Page 465 and 466: EXPRESSIONS Array Creation Expressi
Page 467 and 468: EXPRESSIONS Example: Array Creation
Page 469 and 470: EXPRESSIONS Field Access Using a Pr
Page 471 and 472: EXPRESSIONS Field Access Using a Pr
Page 473 and 474: EXPRESSIONS Accessing Superclass Me
Page 475 and 476: EXPRESSIONS Compile-Time Step 1: De
Page 487 and 488:
EXPRESSIONS Compile-Time Step 2: De
Page 489 and 490:
Page 491 and 492:
Page 493 and 494:
Page 495 and 496:
Page 497 and 498:
Page 499 and 500:
Page 501 and 502:
Page 503 and 504:
Page 505 and 506:
EXPRESSIONS Compile-Time Step 3: Is
Page 507 and 508:
EXPRESSIONS Runtime Evaluation of M
Page 509 and 510:
Page 511 and 512:
Page 513 and 514:
Page 515 and 516:
Page 517 and 518:
EXPRESSIONS Examples: Array Access
Page 519 and 520:
EXPRESSIONS Postfix Increment Opera
Page 521 and 522:
EXPRESSIONS Prefix Increment Operat
Page 523 and 524:
EXPRESSIONS Unary Minus Operator -
Page 525 and 526:
EXPRESSIONS Multiplicative Operator
Page 527 and 528:
EXPRESSIONS Division Operator / 15.
Page 529 and 530:
EXPRESSIONS Remainder Operator % 15
Page 531 and 532:
EXPRESSIONS String Concatenation Op
Page 533 and 534:
EXPRESSIONS String Concatenation Op
Page 535 and 536:
EXPRESSIONS Additive Operators (+ a
Page 537 and 538:
EXPRESSIONS Numerical Comparison Op
Page 539 and 540:
EXPRESSIONS Equality Operators 15.2
Page 541 and 542:
EXPRESSIONS Reference Equality Oper
Page 543 and 544:
EXPRESSIONS Conditional-Or Operator
Page 545 and 546:
EXPRESSIONS Conditional Operator ?
Page 547 and 548:
EXPRESSIONS Simple Assignment Opera
Page 549 and 550:
Page 551 and 552:
Page 553 and 554:
EXPRESSIONS Compound Assignment Ope
Page 555 and 556:
Page 557 and 558:
Page 559 and 560:
EXPRESSIONS Constant Expression 15.
Page 561 and 562:
CHAPTER16 Definite Assignment All t
Page 563 and 564:
DEFINITE ASSIGNMENT Definite Assign
Page 565 and 566:
Page 567 and 568:
DEFINITE ASSIGNMENT The Boolean Ope
Page 569 and 570:
DEFINITE ASSIGNMENT Assignment Expr
Page 571 and 572:
DEFINITE ASSIGNMENT Other Expressio
Page 573 and 574:
DEFINITE ASSIGNMENT Local Variable
Page 575 and 576:
DEFINITE ASSIGNMENT switch Statemen
Page 577 and 578:
DEFINITE ASSIGNMENT for Statements
Page 579 and 580:
DEFINITE ASSIGNMENT try Statements
Page 581 and 582:
Page 583 and 584:
Page 585 and 586:
Page 587 and 588:
CHAPTER17 Threads and Locks And oft
Page 589 and 590:
THREADS AND LOCKS Incorrectly Synch
Page 591 and 592:
THREADS AND LOCKS Memory Model 17.4
Page 593 and 594:
THREADS AND LOCKS Actions 17.4.2
Page 595 and 596:
THREADS AND LOCKS Happens-before Or
Page 597 and 598:
Page 599 and 600:
Page 601 and 602:
THREADS AND LOCKS Executions 17.4.6
Page 603 and 604:
THREADS AND LOCKS Executions and Ca
Page 605 and 606:
THREADS AND LOCKS Observable Behavi
Page 607 and 608:
THREADS AND LOCKS Final Field Seman
Page 609 and 610:
THREADS AND LOCKS Semantics of Fina
Page 611 and 612:
THREADS AND LOCKS Subsequent Modifi
Page 613 and 614:
THREADS AND LOCKS Non-atomic Treatm
Page 615 and 616:
THREADS AND LOCKS Notification 17.8
Page 617 and 618:
THREADS AND LOCKS Sleep and Yield 1
Page 619 and 620:
CHAPTER18 Syntax Is there grammar i
Page 621 and 622:
SYNTAX The Grammar of the Java Prog
Page 623 and 624:
Page 625 and 626:
Page 627 and 628:
Page 629 and 630:
Page 631 and 632:
A abrupt completion See completion,
Page 633 and 634:
definite assignment before, 548 det
Page 635 and 636:
See also numbers literals, term def
Page 637 and 638:
See local class member See member c
Page 639 and 640:
See also hiding; obscuring; scope;
Page 641 and 642:
in assignment conversion context, 9
Page 643 and 644:
of blank final class variables, 199
Page 645 and 646:
interface, multiply inherited, 266
Page 647 and 648:
division, evaluation, 493 equality
Page 649 and 650:
easons why constructors cannot be,
Page 651 and 652:
identity conversion in assignment c
Page 653 and 654:
order, 428 expressions as statement
Page 655 and 656:
L labeled statements identifiers in
Page 657 and 658:
term definition, 122 type, 44 memor
Page 659 and 660:
class, 175 constructor, 241 declara
Page 661 and 662:
conversions of and to See conversio
Page 663 and 664:
importing all public types from a,
Page 665 and 666:
Q superclasses, accessing instances
Page 667 and 668:
internal symbolic reference table,
Page 669 and 670:
declaring class methods with, 216 h
Page 671 and 672:
applicable by subtyping, 445 applic
Page 673 and 674:
unchecked, 301 executed, 409 exit o
Page 675 and 676:
precision, loss of, 81 preparation,
Page 677 and 678:
termination and virtual machine exi
Page 679 and 680:
members and constructors, 55 reifia
Page 681 and 682:
of binary representation, of classe
Page 683 and 684:
Colophon CAMERA-READY electronic co
show all

The Java Language Specification, Third Edition

Create successful ePaper yourself

Delete template?

Save as template?