APPENDIXES

Appendix A

Java Keywords

Appendix B

The ASCII Character Set

Appendix C

Operator Precedence Chart

Appendix D

Java Modifiers

Appendix E

Special Floating-Point Values

Appendix F

Number Systems

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APPENDIX A

Java Keywords

The following fifty keywords are reserved for use by the Java language:

The keywords goto and const are C++ keywords reserved, but not currently used, in Java. This enables Java compilers to identify them and to produce better error messages if they appear in Java programs.

The literal values true, false, and null are not keywords, just like literal value 100. However, you cannot use them as identifiers, just as you cannot use 100 as an identifier.

assert is a keyword added in JDK 1.4 and enum is a keyword added in JDK 1.5.

*The strictfp keyword is a modifier for method or class to use strict floating-point calculations. Floatingpoint arithmetic can be executed in one of two modes: strict or nonstrict. The strict mode guarantees that the evaluation result is the same on all Java Virtual Machine implementations. The nonstrict mode allows intermediate results from calculations to be stored in an extended format different from the standard IEEE floatingpoint number format. The extended format is machine-dependent and enables code to be executed faster. However, when you execute the code using the nonstrict mode on different JVMs, you may not always get precisely the same results. By default, the nonstrict mode is used for floating-point calculations. To use the strict mode in a method or a class, add the strictfp keyword in the method or the class declaration. Strict floatingpoint may give you slightly better precision than nonstrict floating-point, but the distinction will only affect some applications. Strictness is not inherited; that is, the presence of strictfp on a class or interface declaration does not cause extended classes or interfaces to be strict.

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APPENDIX B

The ASCII Character Set

Tables B.1 and B.2 show ASCII characters and their respective decimal and hexadecimal codes. The decimal or hexadecimal code of a character is a combination of its row index and column index. For example, in Table B.1, the letter A is at row 6 and column 5, so its decimal equivalent is 65; in Table B.2, letter A is at row 4 and column 1, so its hexadecimal equivalent is 41.

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TABLE B.1 ASCII Character Set in the Decimal Index

TABLE B.2 ASCII Character Set in the Hexadecimal Index

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APPENDIX C

Operator Precedence Chart

The operators are shown in decreasing order of precedence from top to bottom. Operators in the same group have the same precedence, and their associativity is shown in the table.

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APPENDIX D

Java Modifiers

Modifiers are used on classes and class members (constructors, methods, data, and class-level blocks), but the final modifier can also be used on local variables in a method. A modifier that can be applied to a class is called a class modifier. A modifier that can be applied to a method is called a method modifier. A modifier that can be applied to a data field is called a data modifier. A modifier that can be applied to a class-level block is called a block modifier. The following table gives a summary of the Java modifiers.

*Default access has no modifier associated with it. For example: class Test {}

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APPENDIX E

Special Floating-Point Values

Dividing an integer by zero is invalid and throws ArithmeticException, but dividing a floating-point value by zero does not cause an exception. Floating-point arithmetic can overflow to infinity if the result of the operation is too large for a double or a float, or underflow to zero if the result is too small for a double or a float. Java provides the special floating-point values POSITIVE_INFINITY, NEGATIVE_INFINITY, and NaN (Not a Number) to denote these results. These values are defined as special constants in the Float class and the Double class.

If a positive floating-point number is divided by zero, the result is POSITIVE_INFINITY. If a negative floating-point number is divided by zero, the result is NEGATIVE_INFINITY. If a floating-point zero is divided by zero, the result is NaN, which means that the result is undefined mathematically. The string representation of these three values are Infinity, -Infinity, and NaN. For example,

System.out.print(1.0 / 0); // Print Infinity

System.out.print(–1.0 / 0); // Print –Infinity

System.out.print(0.0 / 0); // Print NaN

These special values can also be used as operands in computations. For example, a number divided by POSITIVE_INFINITY yields a positive zero. Table E.1 summarizes various com-

Note

If one of the operands is NaN, the result is NaN.

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APPENDIX F

Number Systems

1 Introduction

1* 20, respectively:

1 1 0 1 = 1 * 23 + 1 * 22 + 0 * 21 + 1 * 20

23 22 21 20 = 8 + 4 + 0 + 1 = 13

If 7423 is a hex number, the digits 7, 4, 2, and 3 represent 7 * 163, 4 * 162, 2 * 161, and

3* 160, respectively:

7 4 2 3 = 7 * 163 + 4 * 162 + 2 * 161 + 3 * 160

163 162 161 160 = 28672 + 1024 + 32 + 3 = 29731

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718 Appendix F

2 Conversions Between Binary and Decimal Numbers

Tip

The Windows Calculator, as shown in Figure F.1, is a useful tool for performing number conversions. To run it, choose Programs, Accessories, and Calculator from the Start button, then under

View select Scientific.

Decimal Binary

Hex

FIGURE F.1 You can perform number conversions using the Windows Calculator.

Appendix F 719

3 Conversions Between Hexadecimal and Decimal

Numbers

To convert a decimal number d to a hexadecimal number is to find the hexadecimal digits decimal to hex hn, hn- 1, hn- 2, Á , h2, h1, and h0 such that

d= hn * 16n + hn- 1 * 16n- 1 + hn- 2 * 16n- 2 + Á + h2 * 162

+h1 * 161 + h0 * 160

These numbers can be found by successively dividing d by 16 until the quotient is 0. The re-

mainders are h0, h1, h2, Á , hn- 2, hn- 1, and hn.

For example, the decimal number 123 is 7B in hexadecimal. The conversion is done as follows:

07 Quotient

16 7 16 123

0112

711 Remainder

h1 h0

4 Conversions Between Binary and Hexadecimal Numbers