【正文】 Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 1 Chapter 2 Primitive Data Types and Operations Ch a p t e r 1 I n t r o d u c t i o n t o Co m p u t e r s , P r o g ra m s , a n d J a v a Ch a p t e r 2 P ri m i t i v e D a t a T y p e s a n d O p e ra t i o n s Ch a p t e r 4 L o o p s Ch a p t e r 6 A rra y s Ch a p t e r 5 M e t h o d s Ba s i c c o m p u t e r s k i l l s s u c h a s u s i n g W i n d o w s , In t e r n e t E x p l o re r, a n d M i c r o s o f t W o rd 167。167。1 9 .1 1 9 .3 i n C h a p t e r 1 9 R e c u r s i o n Ch a p t e r 2 3 A l g o ri t h m E ffi c i e n c y a n d S o rt i n g Ch a p t e r 3 S e l e c t i o n S t a t e m e n t s Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 2 Objectives ? To write Java programs to perform simple calculations (167。 ). ? To use identifiers to name variables, constants, methods, and classes (167。 ). ? To use variables to store data (167。 ). ? To program with assignment statements and assignment expressions (167。 ). ? To use constants to store permanent data (167。 ). ? To declare Java primitive data types: byte, short, int, long, float, double, and char (167。 – ). ? To use Java operators to write expressions (167。 – ). ? To represent a string using the String type. (167。 ) ? To obtain input using the JOptionPane input dialog boxes (167。 ). ? (Optional) To obtain input from console (167。 ). ? To bee familiar with Java documentation, programming style, and naming conventions (167。 ). ? To distinguish syntax errors, runtime errors, and logic errors (167。 ). ? To debug logic errors (167。 ). Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 3 Introducing Programming with an Example Listing Computing the Area of a Circle This program putes the area of the circle. ComputeArea Run IMPORTANT NOTE: To run the program from the Run button, (1) set c:\Program Files\java\\bin for path, and (2) install slides from the Instructor Resource Website to a directory (., c:\LiangIR) . Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 4 Trace a Program Execution public class ComputeArea { /** Main method */ public static void main(String[] args) { double radius。 double area。 // Assign a radius radius = 20。 // Compute area area = radius * radius * 。 // Display results (The area for the circle of radius + radius + is + area)。 } } no value radius allocate memory for radius animation Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 5 Trace a Program Execution public class ComputeArea { /** Main method */ public static void main(String[] args) { double radius。 double area。 // Assign a radius radius = 20。 // Compute area area = radius * radius * 。 // Display results (The area for the circle of radius + radius + is + area)。 } } no value radius memory no value area allocate memory for area animation Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 6 Trace a Program Execution public class ComputeArea { /** Main method */ public static void main(String[] args) { double radius。 double area。 // Assign a radius radius = 20。 // Compute area area = radius * radius * 。 // Display results (The area for the circle of radius + radius + is + area)。 } } 20 radius no value area assign 20 to radius animation Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 7 Trace a Program Execution public class ComputeArea { /** Main method */ public static void main(String[] args) { double radius。 double area。 // Assign a radius radius = 20。 // Compute area area = radius * radius * 。 // Display results (The area for the circle of radius + radius + is + area)。 } } 20 radius memory area pute area and assign it to variable area animation Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 8 Trace a Program Execution public class ComputeArea { /** Main method */ public static void main(String[] args) { double radius。 double area。 // Assign a radius radius = 20。 // Compute area area = radius * radius * 。 // Display results (The area for the circle of radius + radius + is + area)。 } } 20 radius memory area print a message to the console animation Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, Inc. All rights reserved. 0132221586 9 Identifiers ? An identifier is a sequence of characters that consist of letters, digits, underscores (_), and dollar signs ($). ? An identifier must start with a letter, an underscore (_), or a dollar sign ($). It cannot start with a digit. – An identifier cannot be a reserved word. (See Appendix A, “Java Keywords,” for a list of reserved words). ? An identifier cannot be true, false, or null. ? An identifier can be of any length. Liang, Introduction to Java Programming, Sixth Edition, (c) 2020 Pearson Education, I