Robert Stumpf, Professor

1
Strings

• Robert Stumpf, Professor
• Computer Information Systems
• California State Polytechnic University Pomona

2
Strings

• Basics
• Concatenation
• Behaviors

3
Basics

• Not all languages have a version of strings
• For example C does not have them
• A String is not a primitive data type
• A String is an example of an object

4
Basics

• An object is a collection of primitive data 1
• Thus a String is a collection of characters
• An object has behaviors 1 Note that an object
  may also contain other objects

5
Basics

• The proper way to create a string isString
  myString new String ( abcd)
• An easier way and more popular way isString
  myString abcd

6
Concatenation

• It is defined as the addition or joining of two
  strings into a new String
• For example
• String myString abc def
• String name firstName lastName
• myString has the value of abcdef

7
Concatenation

• Java allows automatic data type conversions in
  the concatenation operation
• For example
• double number 1000.0
• String myString The answer is number
• This is allowed so displaying answers will be
  easy to do to obtain The answer is 1000.0
• The string conversion of number is implicit as
  long as it is not the first argument

8
Behavior

• One can get extract a String or a Character
• String s1 abcdef
• String s2 s1.substring (2) s1 has the
  value of cdef
• String s2 s1.substring (2,4) s2 has
  the value of cd
• char c1 s1.charAt (2) c1 has the value
  of c

9
Behavior

• There are many methods, for example
• String s1 abcdef int temp s1.indexOf
  (c)
• temp has the value of 2
• Note that the argument is a character

10
Behavior

• A String may not be changed
• But a new different string can be created
• For example
• String s1 Abcd
• String s2 s1.toLowerCase ( )
• String s3 s1.toUpperCase ( )
• s2 has the value of abcd
• s3 has the value of ABCD

11
Behavior

• It is important that the operators of !
  not be used in the normal way
• s1.equals (s2)
• not s1.equalsIgnoreCase (s2)
• also one may use
• int temp s1.compares (s2)
• temp 0 //
• temp! 0 // !

12
Summary

• Remember Strings are an object
• An object consists of many primitives which in
  this case are characters
• Strings are easy to create and concatenate
• There are many methods that work with strings

13
Thank You

• Strings Make it Easy to Work with English like
  Data
• Any questions should be directed to Professor
  Robert Stumpf
• Email rvstumpf_at_csupomona.edu
• Web Sitehttp//www.csupomona.edu/rvstumpf