1. Part a: Fundamentals & Class String
MINISTRY OF EDUCATION & HIGHER EDUCATION
COLLEGE OF SCIENCE AND TECHNOLOGY (CST)
KHANYOUNIS- PALESTINE
Computer Programming 2
Lecture 4:
String Processing
Part a: Fundamentals & Class String
Prepared & Presented by:
Mahmoud Rafeek Alfarra

2. (إِنَّ اللَّهَ مَعَ الَّذِينَ اتَّقَوْا وَالَّذِينَ هُمْ مُحْسِنُونَ)
و من يتقِ الله ...
ألا تكفيك هذه ؟!
(إِنَّ اللَّهَ مَعَ الَّذِينَ اتَّقَوْا وَالَّذِينَ هُمْ مُحْسِنُونَ)
(النحل:128)
شريحـة ثابتـة لعلنا نحسن من خلالها أخلاقنـا و أفعالنا لنفوز يوم الامتحان الحقيقي
Downloaded from
Mahmoud Rafeek Alfarra

3. Out Lines Fundamentals of Characters and Strings Class String
String Constructors
String Methods length, charAt and getChars
Comparing Strings
Locating Characters and Substrings in Strings
Extracting Substrings from Strings
Concatenating Strings
Miscellaneous String Methods
String Method valueOf
Downloaded from
Mahmoud Rafeek Alfarra

4. Fundamentals of Characters and Strings
Every program is composed of a sequence of characters thatwhen grouped together meaningfullyare interpreted by the computer as a series of instructions used to accomplish a task.
A character literal is an integer value represented as a character in single quotes.
Downloaded from
Mahmoud Rafeek Alfarra

5. Fundamentals of Characters and Strings
The value of a character literal is the integer value of the character in the Unicode character set.
String literals are stored in memory as String objects.
Downloaded from
Mahmoud Rafeek Alfarra

6. ASCII Character Set A = 65 Downloaded from http://staff.cst.ps/mfarra
Mahmoud Rafeek Alfarra

7. String in Java String Class StringBuffer Class StringTokenizer Class
Downloaded from
Mahmoud Rafeek Alfarra

8. Class String Class String is a pre-defined class in Java
Class String is used to represent strings in Java which has many capabilities.
We can declare an object of string with out Constructor as:
String x = “Ahmad”
Downloaded from
Mahmoud Rafeek Alfarra

9. String Constructors
Class String provides constructors for initializing String objects in a variety of ways.
Downloaded from
Mahmoud Rafeek Alfarra

10. length, charAt and getChars
Class String has many operations to manipulate strings.
Length: return the length of a string
String y = "Mahmoud Rafeek Alfarra";
System.out.print(y.length());
Will print : 22
Downloaded from
Mahmoud Rafeek Alfarra

11. length, charAt and getChars
Class String has many operations to manipulate strings.
charAt : obtain the character at a specific location in a string.
String y = "Mahmoud Rafeek Alfarra";
System.out.println(y.charAt(0));
System.out.println(y.charAt(1));
Will print : M a
Downloaded from
Mahmoud Rafeek Alfarra

12. length, charAt and getChars
Class String has many operations to manipulate strings.
getChars: retrieve a set of characters from a string as a char array.
char [] ret = new char [5] ;
String y = "Mahmoud Rafeek Alfarra";
y.getChars(0,3,ret,0);
Will stor mah in ret
Will print m a h
for(int i=0; i<5; i++)
System.out.println(ret[i]);
Downloaded from
Mahmoud Rafeek Alfarra

13. Comparing Strings
Class String provides several methods for comparing strings.
Equals: compare if two strings are identical.
equalsIgnoreCase: ignores whether the letters in each string are uppercase or lowercase.
compareTo: does not ignore the case
regionMatches: compare portions of two strings for equality.
Downloaded from
Mahmoud Rafeek Alfarra

14. Comparing Strings
Class String provides several methods for comparing strings.
Equals:
String s1 = "Ali";
System.out.println(s1.equals("Ala"));
Will print
false
Downloaded from
Mahmoud Rafeek Alfarra

15. Comparing Strings
Class String provides several methods for comparing strings.
equalsIgnoreCase
String s1 = "Ali";
System.out.println(s1.equalsIgnoreCase("ali"));
Will print
true
Downloaded from
Mahmoud Rafeek Alfarra

16. Comparing Strings
Class String provides several methods for comparing strings.
compareTo: does not ignore the case
String s1 = "zain";
System.out.println(s1.compareTo("hussam"));
Will print
negative
String s1 = “ahmad";
System.out.println(s1.compareTo("hussam"));
Will print
Positive
String s1 = "zain";
System.out.println(s1.compareTo(“zain"));
Will print
Downloaded from
Mahmoud Rafeek Alfarra

17. Comparing Strings
Class String provides several methods for comparing strings.
regionMatches:
String s1 = "Mahmoud";
System.out.println(s1.regionMatches(3,"lmoud",1,4));
Will print
true
Downloaded from
Mahmoud Rafeek Alfarra

18. Locating Characters and Substrings in Strings
lastIndexOf and indexOf are methods to detect the position of substrings in any string.
String s1 = "Mahmoud Rafeek Alfarra";
System.out.println(s1.lastIndexOf("a"));
System.out.println(s1.indexOf("a"));
Will print 21 1
Downloaded from
Mahmoud Rafeek Alfarra

19. Extracting Substrings from Strings
Class String provides two substring methods to enable a new String object to be created by copying part of an existing String object. Each method returns a new String object.
String s1 = "Mahmoud Rafeek Alfarra";
System.out.println(s1.substring(0,3)); System.out.println(s1.substring(12));
Will print
Mah
ek Alfarra
Downloaded from
Mahmoud Rafeek Alfarra

20. Concatenating Strings
String method concat concatenates two String objects and returns a new String object containing the characters from both original strings.
String s1 = "Mahmoud ";
String s2 = "Rafeek ";
String s3 = s1.concat(s2); System.out.println(s3);
Will print
Mahmoud Rafeek
Downloaded from
Mahmoud Rafeek Alfarra

21. Miscellaneous String Methods
Replace: replace substring with substring
toLowerCase: generate a new String object with lowercase letters
toUpperCase: generate a new String object with uppercase letters .
trim: removes all whitespace characters that appear at the beginning or end of the string
toCharArray: to create a new character array containing a copy of the characters in string
Downloaded from
Mahmoud Rafeek Alfarra

22. Case Study valueOf Textbook chapter 29 Page 1365
Downloaded from
Mahmoud Rafeek Alfarra

23. Class StringBuffer Next Lecture …
Downloaded from
Mahmoud Rafeek Alfarra