Presentation is loading. Please wait.

Presentation is loading. Please wait.

Strings, Characters and Regular Expressions

Published byReynold Bruce Modified over 6 years ago

Similar presentations

Presentation on theme: "Strings, Characters and Regular Expressions"— Presentation transcript:

1 Strings, Characters and Regular Expressions
29 Strings, Characters and Regular Expressions

2 Outline StringConstructors .java Line 12 Line 13 Line 14 Line 15
Program output

3 Outline (1 of 2) Line 15 Lines 20-21
StringMiscellaneou s.java (1 of 2) Line 15 Lines 20-21 Determine number of characters in String s1 Display the characters of the string s1 in reverse order

4 Copy (some of) s1’s characters to charArray
Outline StringMiscellaneou s.java (2 of 2) Line 24 Program output

5 29.3.3 Comparing Strings Comparing String objects Method equals
Method equalsIgnoreCase Method compareTo Method regionMatches

6 Outline StringCompare.java (1 of 3) Line 17 Line 23 Method equals tests two objects for equality using lexicographical comparison Equality operator (==) tests if both references refer to same object in memory

7 Test two objects for equality, but ignore case of letters in Strings
Outline StringCompare.java (2 of 3) Line 29 Lines 36-44 Line 47 Method compareTo compares String objects Method regionMatches compares portions of two String objects for equality

8 Outline StringCompare.java (3 of 3) Program output

9 Common Programming Error 29.2
Comparing references with == can lead to logic errors, because == compares the references to determine whether they refer to the same object, not whether two objects have the same contents. When two identical (but separate) objects are compared with ==, the result will be false. When comparing objects to determine whether they have the same contents, use method equals.

10 Outline StringStartEnd.java (1 of 2) Lines 13 and 22 Method startsWith determines if String starts with specified characters

11 Method endsWith determines if String ends with specified characters
Outline Method endsWith determines if String ends with specified characters StringStartEnd.java (2 of 2) Line 32 Program output

12 29.3.4 Locating Characters and Substrings in Strings
Search for characters in String Method indexOf Method lastIndexOf

13 Outline (1 of 3) Lines 12, 14 and 16 Lines 20, 22 and 24
StringIndexMethods .java (1 of 3) Lines 12, 14 and 16 Lines 20, 22 and 24 Method indexOf finds first occurrence of character in String Method lastIndexOf finds last occurrence of character in String

14 Outline Methods indexOf and lastIndexOf can also find occurrences of substrings StringIndexMethods .java (2 of 3) Lines 28, 30, 32, 36, 38 and 40

15 Outline StringIndexMethods .java (3 of 3) Program output

16 29.3.5 Extracting Substrings from Strings
Create Strings from other Strings Method substring

17 Outline Beginning at index 20, extract characters from String letters
SubString.java Line 12 Line 15 Program output Beginning at index 20, extract characters from String letters Extract characters from index 3 to 6 from String letters

18 29.3.6 Concatenating Strings
Method concat Concatenate two String objects

19 Outline Concatenate String s2 to String s1
StringConcatenatio n.java Line 13 Line 14 Program output Concatenate String s2 to String s1 However, String s1 is not modified by method concat

20 29.3.7 Miscellaneous String Methods
Return modified copies of String Return character array

21 Use method trim to return s3 copy in which whitespace is eliminated
Outline StringMiscellaneou s2.java (1 of 2) Line 16 Line 19 Line 20 Line 23 Use method replace to return s1 copy in which every occurrence of ‘l’ is replaced with ‘L’ Use method toUpperCase to return s1 copy in which every character is uppercase Use method toLowerCase to return s2 copy in which every character is uppercase Use method trim to return s3 copy in which whitespace is eliminated

22 Use method toCharArray to return character array of s1
Outline StringMiscellaneou s2.java (2 of 2) Line 26 Program output

23 29.3.8 String Method valueOf String provides static class methods
Returns String representation of object, data, etc.

24 Outline StringValueOf.java (1 of 2) Line 12 Line 13

25 Outline static method valueOf of class String returns String representation of various types StringValueOf.java (2 of 2) Lines 18-29 Program output

26 29.4 Class StringBuffer Class StringBuffer
When String object is created, its contents cannot change Used for creating and manipulating dynamic string data i.e., modifiable Strings Can store characters based on capacity Capacity expands dynamically to handle additional characters Uses operators + and += for String concatenation

27 Performance Tip 29.2 Java can perform certain optimizations involving String objects (such as sharing one String object among multiple references) because it knows these objects will not change. Strings (not StringBuffers) should be used if the data will not change.

28 Performance Tip 29.3 In programs that frequently perform string concatenation, or other string modifications, it is more efficient to implement the modifications with class StringBuffer (covered in Section 29.4).

29 Outline

30 Only 10 characters from StringBuffer are printed
Outline StringBufferCapLen .java Line 11 Line 13 Line 16 Program output Only 10 characters from StringBuffer are printed

31 Performance Tip 29.4 Dynamically increasing the capacity of a StringBuffer can take a relatively long time. Executing a large number of these operations can degrade the performance of an application. If a StringBuffer is going to increase greatly in size, possibly multiple times, setting its capacity high at the beginning will increase performance.

32 Outline StringBufferChars. java (1 of 2) Line 12 Line 15

33 (2 of 2) Lines 21 and 22 Line 25 Program output
StringBufferChars. java (2 of 2) Lines 21 and 22 Line 25 Program output

34 Common Programming Error 29.3
Attempting to access a character that is outside the bounds of a StringBuffer (i.e., with an index less than 0 or greater than or equal to the StringBuffer’s length) results in a StringIndexOutOfBoundsException.

35 29.4.4 StringBuffer append Methods
Method append Allow data values to be added to StringBuffer

36 Outline StringBufferAppend .java (1 of 3)

37

38 Outline StringBufferAppend .java (3 of 3) Program output

39 29.4.5 StringBuffer Insertion and Deletion Methods
Method insert Allow data-type values to be inserted into StringBuffer Methods delete and deleteCharAt Allow characters to be removed from StringBuffer

40 Outline StringBufferInsert .java (1 of 3)

41 Use method insert to insert data in beginning of StringBuffer
Outline StringBufferInsert .java (2 of 3) Lines 20-38 Use method insert to insert data in beginning of StringBuffer

42 Outline (3 of 3) Line 43 Line 44 Program output
StringBufferInsert .java (3 of 3) Line 43 Line 44 Program output

43 29.5 Class Character Treat primitive variables as objects
Type wrapper classes Boolean Character Double Float Byte Short Integer Long We examine class Character

44 Obtain first character of the input string
Outline StaticCharMethods. java (1 of 3) Line 12 Obtain first character of the input string

45 Outline Determine whether c is defined Unicode character set
Determine whether c is defined Unicode digit Determine whether c can be used as first character in identifier StaticCharMethods. java (2 of 3) Line 15 Line 16 Line 18 Line 20 Line 21 Line 23 Lines 25 and 27 Lines 29 and 31 Determine whether c can be used as identifier character Determine whether c is a letter Determine whether c is letter or digit Determine whether c is lowercase and uppercase, respectively Convert c to its uppercase and lowercase, respectively

46 Outline StaticCharMethods. java (3 of 3) Program output

47 Outline OtherCharMethods.j ava Lines 8-9 Line 12 Line 14 Program output Assign two character literals to two Character objects. Auto-boxing occurs. Obtain the char value stored in Character object c1 Method toString returns a string representation of the Character object Use method equals to determine whether c1 has the same contents as c2

Download ppt "Strings, Characters and Regular Expressions"

Similar presentations

Purpose : To convert this string to a new character array. Return Type : char[ ] Parameters : none Declaration : public char[ ] toCharArray() Returns.

Purpose : To convert this string to a new character array. Return Type : char[ ] Parameters : none Declaration : public char[ ] toCharArray() Returns.
Liang, Introduction to Java Programming, Ninth Edition, (c) 2013 Pearson Education, Inc. All rights reserved. 1 Chapter 9 Strings.

Liang, Introduction to Java Programming, Ninth Edition, (c) 2013 Pearson Education, Inc. All rights reserved. 1 Chapter 9 Strings.
Strings in Java 1. strings in java are handled by two classes String &

Strings in Java 1. strings in java are handled by two classes String &
Chapter 7 Strings F To process strings using the String class, the StringBuffer class, and the StringTokenizer class. F To use the String class to process.

Chapter 7 Strings F To process strings using the String class, the StringBuffer class, and the StringTokenizer class. F To use the String class to process.
1 Working with String Duo Wei CS110A_004. 2 Empty Strings An empty string has no characters; its length is 0. Not to be confused with an uninitialized.

1 Working with String Duo Wei CS110A_ Empty Strings An empty string has no characters; its length is 0. Not to be confused with an uninitialized.
1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.
Chapter 7 Strings F Processing strings using the String class, the StringBuffer class, and the StringTokenizer class. F Use the String class to process.

Chapter 7 Strings F Processing strings using the String class, the StringBuffer class, and the StringTokenizer class. F Use the String class to process.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 1 Chapter 8 Strings.

Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved Chapter 8 Strings.
Java Programming Strings Chapter 7.

Java Programming Strings Chapter 7.
Strings An extension of types A class that encompasses a character array and provides many useful behaviors Chapter 9 Strings are IMMUTABLE.

Strings An extension of types A class that encompasses a character array and provides many useful behaviors Chapter 9 Strings are IMMUTABLE.
©2004 Brooks/Cole Chapter 7 Strings and Characters.

©2004 Brooks/Cole Chapter 7 Strings and Characters.
Chapter 9 Characters and Strings. Topics Character primitives Character Wrapper class More String Methods String Comparison String Buffer String Tokenizer.

Chapter 9 Characters and Strings. Topics Character primitives Character Wrapper class More String Methods String Comparison String Buffer String Tokenizer.
©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter 9 - 1 Chapter 9 Characters and Strings (sections 9.1-9.2,

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Chapter 9 Characters and Strings (sections ,
CSM-Java Programming-I Spring,2005 String Handling Lesson - 6.

CSM-Java Programming-I Spring,2005 String Handling Lesson - 6.
Fundamental Programming Structures in Java: Strings.

Fundamental Programming Structures in Java: Strings.
Strings, Etc. Part I: Strings. About Strings There is a special syntax for constructing strings: Hello Strings, unlike most other objects, have a defined.

Strings, Etc. Part I: Strings. About Strings There is a special syntax for constructing strings: "Hello" Strings, unlike most other objects, have a defined.
28-Jun-15 String and StringBuilder Part I: String.

28-Jun-15 String and StringBuilder Part I: String.
©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter 9 - 1 Chapter 9 Characters and Strings (sections 9.1-9.2,

©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 th Ed Chapter Chapter 9 Characters and Strings (sections ,
 1992-2007 Pearson Education, Inc. All rights reserved. 1 30 Strings, Characters and Regular Expressions.

 Pearson Education, Inc. All rights reserved Strings, Characters and Regular Expressions.
 2003 Prentice Hall, Inc. All rights reserved. Chapter 11 – Strings and Characters Outline 11.1 Introduction 11.2 Fundamentals of Characters and Strings.

 2003 Prentice Hall, Inc. All rights reserved. Chapter 11 – Strings and Characters Outline 11.1 Introduction 11.2 Fundamentals of Characters and Strings.

Similar presentations

Ads by Google