Java程序設(shè)計英文版課件：ch13 Strings

1、1Chapter 13Strings 2Strings manipulation is one of the most common activities in computer programmingClass: StringClass: StringBufferClass: StringBuilderRegular expressions 3Introductionjava.lang.String Objects of the String class are immutable “XXXXX” is a object of the Class StringConstructor summ

2、ary of Class String String(byte bytes); String(char value); String(String original); String(StringBuffer buffer);4A example of class String： public class Test public static void main (String args) String s1 = hello; String s2 = world; String s3 = hello; System.out.println(s1 = s3); /true s1 = new St

3、ring (hello); s2 = new String (hello) ; System.out.println(s1 = s2); /false System.out.println(s1.equals(s2); /true char c = s,u,n, ,j,a,v,a; String s4 = new String(c); String s5 = new String(c,4,4); System.out.println(s4); /sun java System.out.println(s5); /java 5A example of class String：6A exampl

4、e of class String：7Methods summary of class String public char charAt(int index)public int length()public int indexOf(String str)public int indexOf(String str,int fromIndex)public boolean equalsIgnoreCase(String another)public String replace(char oldChar,char newChar)8A example of class String： publ

5、ic class Test public static void main (String args) String s1 = sun java, s2 = Sun Java; System.out.println(s1.charAt(1) ;/uSystem.out.println(s2.length() ;/8System. out. println (s1. indexOf (java) ) ; / 4System. out. println (s1. indexOf (Java) ) ; / -1System.out.println(s1.equals(s2) ;/falseSyste

6、m.out.println(s1.equalsIgnoreCase(s2); /trueString s = “He is a student. He is studying java now.;String sr = s.replace(He,She) ;System.out.println(sr) ; /Output She is a student. She is studying java now.9Methods summary of class String public boolean startsWith(String prefix)public boolean endsWit

7、h(String suffix)public String toUpperCase()public String toLowerCase()public String substring(int beginlndex)public String substring(int beginlndex,int endlndex)public String trim()10A example of class String： public class Test public static void main (String args) String s = Welcome to Java World!;

8、String s1 = sun java ;System. out .println (s.startsWith(Welcome); /trueSystem. out .println (s.endsWith(World); /falseString sL = s.toLowerCase();String sU = s.toUpperCase();System.out.println(sL) ;/welcome to java world!System.out.println(sU) ;/WELCOME TO JAVA WORLD!String subS = s.substring(11);S

9、ystem.out.println(subS) ;/Java World!String sp = s1.trim();System.out.println(sp) ;/sun java 11Methods summary of class String public static String valueOf (Object obj) public static String valueOf (boolean b) public static String valueOf (char c) public static String valueOf (int i) public static S

10、tring valueOf (long l)public string split(string regex) The method splits the string to an array of string by a specified string12public class Test public static void main(String args) int j = 1234567 ; String sNumber = String.valueOf(j) ; System.out.println(j have +sNumber.length()+ bits) ; String

11、s = Mary,F,1976; String sPlit = s.split(,); for (int i=0;isPlit.length;i+) System.out.println(sPliti) ; Output:j have 7 bitsMaryF197613Introductionjava.lang.StringBuffer A thread-safe, mutable sequence of characters. A string buffer is like a String, but can be modified.Constructor summary of Class

12、StringBuffer StringBuffer() StringBuffer(String str) 14Methods summary of class StringBuffer public StringBuffer append (.) public StringBuffer append(String str) public StringBuffer append(StringBuffer sbuf) public StringBuffer append(char str) public StringBuffer append (char str, int offset, int

13、len) public StringBuffer append(double d) public StringBuffer append(Object obj)Appends the string representation of the any argument to this sequence. (Object.tostring)15Methods summary of class StringBuffer public StringBuffer insert ( . ) Inserts the string representation of the any argument into

14、 this sequence. public StringBuffer insert(int offset, long l) public StringBuffer insert(int offset, double d)public StringBuffer delete (int start, int end) Removes the characters in a substring of this sequence. 16Methods summary of class StringBuffer Some methods similar as class String public i

15、nt indexOf(string str) public int indexOf(string str, int fromlndex) public String substring(int start) public String substring(int start, int end) public int length()public StringBuffer reverse () Causes this character sequence to be replaced by the reverse of the sequence. 17public class Test publ

16、ic static void main(String args) String s = Mircosoft; char a = a,b,c ; StringBuffer sbl = new StringBuffer(s); sbl.append (/).append(IBM).append(/).append (Sun); System.out.println(sbl) ; StringBuffer sb2 = new StringBuffer(nu); for(int i = 0;i=9;i+) sb2.append(i) ; System.out.println(sb2) ; sb2.de

17、lete(8,sb2.length().insert(0,a); System.out.println(sb2) ; System.out.println(sb2.reverse() ; Output: Mircosoft/IBM/Sunnu0123456789abcnu012345543210uncba18Introductionjava.lang.StringBuilder A mutable sequence of characters. No guarantee of synchronization. Used by a single thread Faster than String

18、BufferConstructor summary of Class StringBuffer StringBuilder() StringBuilder(String str) 19import java.util.*;public class UsingStringBuilder public static Random rand = new Random(47); public String toString() StringBuilder result = new StringBuilder(); for(int i = 0; i 5; i+) result.append(rand.n

19、extInt(100); result.append(, ); result.delete(result.length()-2, result.length(); result.append(); return result.toString(); public static void main(String args) UsingStringBuilder usb = new UsingStringBuilder(); System.out.println(usb); Output: 58, 55, 93, 61, 6120The different between String and S

20、tringBuilder21The different between String and StringBuilder22The different between String and StringBuilder23The different between String and StringBuilder24public class AppendStringTest public static void main(String args) String text = ; long beginTime = System.currentTimeMillis(); for(int i = 0;

21、 i 10000; i+) text = text + i; long endTime = System.currentTimeMillis(); System.out.println( Run Time： + (endTime - beginTime); StringBuilder builder = new StringBuilder( ); beginTime = System.currentTimeMillis(); for(int i = 0; i 10000; i+) builder.append(String.valueOf(i); endTime = System.curren

22、tTimeMillis(); System.out.println( Run Time： + (endTime - beginTime); 25text = text + i; -StringBuilder builder = new StringBuilder(text);builder.append(String.valueOf(i);text = builder.tostring(); 26 IntroductionRegular expressions have long been integral to standard Unix utilities like sed and awk

23、, and languages like Python and Perl Allow you to specify, programmatically, complex patterns of text that can be discovered in an input string. Solve all sorts of string processing, matching and selection, editing, and verification problems in a completely general way. 27 Character Classes：? /might

24、 or might not be appeared s /A whitespace character (space, tab, newline, form feed, carriage return) S /A non-whitespace character (s)d /A numeric digit 0-9 D /A non-digit o-9 w /A word character a-zA-Z_0-9 W /A non-word character w 28 Character Classes：. /Any character abc /Any of the characters a

25、, b, or c (same as a|b|c)abc /Any character except a, b, and c (negation) a-zA-Z /Any character a through z or A through Z (range) abchij /Any of a,b,c,h,I,j (same as a|b|c|h|i|j) (union) a-z&hij /Either h, i, or j (intersection) 29 A example of Regular expressions ：public class IntegerMatch pub

26、lic static void main(String args) System.out.println(-1234.matches(-?d+); System.out.println(5678.matches(-?d+); System.out.println(+911.matches(-?d+); System.out.println(+911.matches(-|+)?d+); /* Output:truetruefalsetrue */30 A example of Regular expressions ：import java.util.*;public class Splitti

27、ng public static String knights = Then, when you have found the shrubbery, you must + cut down the mightiest tree in the forest. + with. a herring!; public static void split(String regex) String arrayString = knights.split(regex); for(int i=0;iarrayString.length;i+) System.out.println(arrayStringi);

28、 31 A example of Regular expressions ：public static void main(String args) /split( ); / Doesnt have to contain regex chars /split(W+); / Non-word characters split(nW+); / n followed by non-word characters /Output:Thewheyou have found the shrubbery, you must cut dowthe mightiest tree ithe forest. wit

29、h. a herring!32 A example of Regular expressions ：public class Replacing static String s = Splitting.knights; public static void main(String args) System.out.println(s); System.out.println(s.replaceFirst(fw+, located); System.out.println(s.replaceAll(shrubbery|tree|herring,banana); /Output:Then, whe

30、n you have found the shrubbery, you must cut down the mightiest tree in the forest. with. a herring!Then, when you have located the shrubbery, you must cut down the mightiest tree in the forest. with. a herring!Then, when you have found the banana, you must cut down the mightiest banana in the forest. with. a banana!33 Two classesjava.util.regex Pattern A compiled representation of a regular expression. Matcher