ICS11 Introduction to Computer Programming II

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Xavier University Computer Center Sun
Microsystems, Philippines
Java sa Eskwela (JsE) Program

• ICS11 Introduction to Computer Programming II
• Joselito dela Cruz Ty

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Chapter 10
Strings and Characters
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Outline
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chars and Characters

• In Java there are two types of variables
• Objects
• e.g. Point, JApplet, String
• Native data types
• e.g. int, float, double, long, byte, char
• char is a native data type it is a number
  between 0-255

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chars and Characters

• Examples of char
• a
• b
• c
• Etc
• Every char can be represented as an integer from
  1 to 255
• See Appendix D ASCII Character Set

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chars and Characters

• Exercise1 Create a program that outputs the
  letters a-z in the Standard output
  (System.out.println)
• Exercise2 Create a program that creates 26
  buttons labeled with the letters A-Z
• Exercise3 Add a textfield in your previous
  program whenever you click a letter, the letter
  gets added into the textfield

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chars and Characters

• Because char is a native data type, it is not an
  Object
• It does not define methods to perform operations
  on it
• To perform operations on a char, use the methods
  define in class Character

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Characters

• Methods of class Character (p489)
• isDefined()
• isDigit()
• isLetter()
• isLetterOrDigit()
• isLowerCase()
• isUpperCase()
• toUpperCase()
• toLowerCase()

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Characters

• Exercise Add a KeyboardListener to your previous
  program so that the user can use the keyboard to
  press the letters in the frame

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Strings

• A String in Java is not a native data type it is
  an Object
• Other programming languages represent a String as
  an array of chars
• Samples of Strings
• hello
• Happy New Year!
• Etc
• Therefore, Strings have instance variables,
  methods, and constructors

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Strings

• A String is usually created this way
• String nameSnuffleupagus
• A String can also be created using its
  constructors (see pp.459-461)

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String Methods

• length()
• charAt()
• getChars()
• equals()
• equalsIgnoreCase()
• regionMatches()
• indexOf()
• lastIndexOf()

• substring()
• replace()
• toLowerCase()
• toUpperCase()
• trim()
• valueOf()

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String Methods

• Exercise from the code below, output separately
  the first name and the last names
• String nameSantos, Carlo, dela Cruz,
  Jose, Concepcion, Miguel Fernando
• String nameSantos, Carlo dela Cruz, Jose
  Concepcion, Miguel Fernando

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Type Conversion

• Any native data type and any object can be
  converted to String by using the method
  .toString()
• What is the code to convert from each of the
  following data types
• int
• char
• String

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StringBuffer

• A limitation of a String object is that it can
  not be changed once it is created
• A StringBuffer allows dynamic changing of String
  information

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StringBuffer

• Methods of class StringBuffer
• charAt()
• setCharAt()
• deleteCharAt()
• delete()
• getChars()
• reverse()
• append()
• insert()

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StringTokenizer

• Breaks down String elements into tokens or
  words
• Methods
• countTokens()
• hasMoreTokens()
• nextToken()