JETT Workshop - Java Basics

Strings
(Example code and figures from Computing Concepts with Java Essentials, 3rd edition, by Cay Horstmann.
Visit www.wiley.com/college/horstmann for information on the current edition of this excellent text.)

from the AP CS Java Subset
- Students need not be aware that strings are composed of char values.
  - Introducing char does not increase the expressiveness of the subset.
  - Not introducing char avoids complexities with the char/int conversions and confusion between "x" and 'x'.
- Students need to understand string concatenation, String.substring, and String.equals.
- String concatenation + is part of the AP Java subset.
  - Students are expected to know that concatenation converts numbers to strings and invokes toString on objects.
  - String concatenation can be less efficient than using the StringBuffer class.
  - However, for greater simplicity and conceptual clarity, the StringBuffer class is not in the subset.
- The escape sequences inside strings \\, \", \n are part of the AP Java subset.
  - The \t escape and Unicode \uxxxx escapes are not in the subset.
  - The \' escape is only necessary inside character literals and is not in the subset.
- Processing string input (e.g., with StringTokenizer) and converting strings to numeric values (e.g., with Integer.parseInt) is not in the subset.

String is a class, and strings are objects in Java
String constants (this shorthand notation actually creates a String object)
"Carl"
String variables (name holds a reference to a String object)
String name = "Carl";
String length (length( ) is a method in the String class)
int n = name.length();

String fname = "Harry"; String lname = "Hacker"; String name = fname + lname;
name is "HarryHacker"
If one operand of + is a string, the other is converted to a string:
String a = "Agent"; String name = a + 7;
name is "Agent7"

String greeting = "Clown"; String sub = greeting.substring(1, 4);
sub is "low"
Supply start and the position after the last character

First position is at 0

C	l	o	w	n
0	1	2	3	4