Strings v.1.1

Strings and Strings Manipulation

Contents ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Contents (2) ,[object Object],[object Object],[object Object]

What Is String? ,[object Object],[object Object],[object Object],[object Object],[object Object],String s = "Hello, Java"; s H e l l o , J a v a

java.lang.String ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

java.lang.String (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],String s = "Hello!"; int len = s. l ength () ; // len = 6 char ch = s .charAt(1) ; // ch = 'e' index = s.charAt(index) = 0 1 2 3 4 5 H e l l o !

Strings – First Example String s = "Stand up, stand up, Balkan superman."; System.out.printf("s = amp;quot;%samp;quot;%n", s); System.out.printf("s. l ength () = %d%n", s.length()); for (int i = 0; i < s.length(); i++) { System.out.printf("s[%d] = %c%n", i, s.charAt(i)); }

Strings – First Example Live Demo

Declaring, Creating, Reading and Printing Creating and Using Strings

Declaring Strings ,[object Object],String str;

Creating Strings ,[object Object],[object Object],[object Object],[object Object],[object Object]

Creating Strings (2) ,[object Object],[object Object],[object Object],[object Object],S tring s; // s is equal to null St ring s = "I am string literal!"; S tring s 2 = s; String s = "I'm " + 42 + " years old.";

Reading And Printing Strings ,[object Object],[object Object],String s = input.nextLine(); ,[object Object],[object Object],System.out.print("Please enter your name: "); String name = input.nextLine(); System.out.printf("Hello, %s!%n", name);

Live Demo Reading and Printing Strings

Manipulating Strings Comparing, Concatenating, Searching, Extracting Substrings, Splitting

Comparing Strings ,[object Object],[object Object],[object Object],[object Object],int result = str1.compareToIgnoreCase(str2); // result == 0 if str1 equals str2 // result < 0 if str1 if before str2 // result > 0 if str1 if after str2 str1.compareTo(str2);

Comparing Strings (2) ,[object Object],[object Object],[object Object],[object Object],if (str1.equalsIgnoreCase(str2)){ … } if (str1.equals(str2)){ … }

Comparing Strings (3) ,[object Object],[object Object],[object Object],String str1 = new String("Hello"); String str2 = str1; System.out.println((str1==str2)); // true String str1 = "Hello"; String str2 = "Hello"; System.out.println((str1==str2)); // true !!! String str1 = new String("Hello"); String str2 = new String("Hello"); System.out.println((str1==str2)); // This is false !

Comparing Strings – Example ,[object Object],String[] towns = {"Sofia", "Varna", "Plovdiv", "Pleven", "Bourgas", "Rousse", "Yambol"}; String firstTown = towns[0]; for (int i=1; i<towns. l ength; i++) { String currentTown = towns[i]; if (currentTown.compareTo(firstTown) < 0) { firstTown = currentTown; } } System.out.println("First town: " + firstTown);

Concatenating Strings ,[object Object],[object Object],[object Object],[object Object],S tring str = str1. c oncat(str2); String str = str1 + str2 + str3; String str += str1; S tring n ame = " Peter "; int age = 22 ; S tring s = name + " " + age ; //  "Peter 22"

Concatenating Strings – Example String firstName = "Svetlin"; String lastName = "Nakov"; String fullName = firstName + " " + lastName; System.out.println(fullName); int age = 2 6 ; String nameAndAge = "Name: " + fullName + "Age: " + age; System.out.println(nameAndAge); // Name: Svetlin Nakov // Age: 2 6

Concatenating Strings Live Demo

Searching Strings ,[object Object],[object Object],[object Object],[object Object],[object Object],i ndexOf( S tring str) i ndexOf( S tring str, int from Index) l astIndexOf( S tring) lastIndexOf(String, int fromIndex)

Searching Strings – Example String str = "Java Programming Course"; int index = str.indexOf("Java"); // index = 0 index = str.indexOf("Course"); // index = 17 index = str.indexOf("COURSE"); // index = -1 // indexOf is case sensetive. -1 means not found index = str.indexOf("ram"); // index = 9 index = str.indexOf("r"); // index = 6 index = str.indexOf("r", 7); // index = 9 index = str.indexOf("r", 10); // index = 20 i = s.charAt(i) = 0 1 2 3 4 5 6 7 8 9 10 11 12 … J a v a P r o g r a m m …

Extracting Substrings ,[object Object],[object Object],[object Object],[object Object],S tring filename = "C: ics ila2005.jpg"; S tring name = filename. s ub s tring(8, 16 ); // name is Rila2005 S tring filename = "C: ics ummer2005.jpg"; S tring nameAndExtension = filename. s ub s tring(8); // nameAndExtension is Rila2005 .jpg 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 C : P i c s R i l a 2 0 0 5 . j p g

Extracting Substrings Live Demo

Splitting Strings ,[object Object],[object Object],[object Object],String[] split(String regex) String[] parts = "Ivan; Petar,Gosho".split("[;,]"); // this wil separate the stirng into three parts // "Ivan", " Petar" and "Gosho"

Splitting Strings - Example String listOfBeers = "Amstel, Zagorka, Tuborg, Becks."; String[] beers = listOfBeers.split("[ ,.]"); System.out.println("Available beers are:"); for (String beer : beers) { if (!"".equalsIgnoreCase(beer)) { System.out.println(beer); } }

Other String Operations Replacing Substrings, Changing Character Casing, Trimming

Replacing Substrings ,[object Object],[object Object],String cocktail = "Vodka + Martini + Cherry"; String replaced = cocktail.replace("+", "and"); // Vodka and Martini and Cherry

Changing Character Casing ,[object Object],[object Object],S tring alpha = "aBcDeFg"; S tring lowerAlpha = alpha. t oLower Case (); // abcdefg System.out.println(lowerAlpha); S tring alpha = "aBcDeFg"; S tring upper A lpha = alpha. t oUpper Case (); // ABCDEFG System.out.println(upperAlpha);

Trimming White Space ,[object Object],String s = " example of white space "; String clean = s.trim(); System.out.println(clean);

Other String Operations Live Demo

Building and Modifying Strings Using StringBuilder C lass

Constructing Strings ,[object Object],[object Object],[object Object],[object Object],public static s tring d upChar(char ch, int count){ S tring result = ""; for (int i=0; i<count; i++) result += ch; return result; } Bad practice. Avoid this!

Changing the Contents of a String – StringBuilder ,[object Object],[object Object],public static String r everseIt(String s) { StringBuilder sb = new StringBuilder(); for (int i = s.length()-1; i >= 0; i--) sb.append(s.charAt(i)); return sb.ToString(); }

The StringBuilde r Class ,[object Object],[object Object],StringBuilder : length() = 11 capacity() = 15 used buffer (length()) unused buffer Capacity H e l l o , J a v a !

The StringBuilde r Class (2) ,[object Object],[object Object],[object Object],[object Object],[object Object]

The StringBuilde r Class (3) ,[object Object],[object Object],[object Object],[object Object],[object Object]

StringBuilder – Example ,[object Object],public static String extractCapitals(String s) { StringBuilder result = new StringBuilder(); for (int i = 0; i < s.length(); i++) { char ch = s.charAt(i); if (Character.isUpperCase(ch)) { result.append(ch); } } return result.toString(); }

How the + Operator Does String Concatenations? ,[object Object],[object Object],[object Object],[object Object],String result = str1 + str2; StringBuffer sb = new StringBuffer(); sb. a ppend(str1); sb. a ppend(str2); S tring result = sb. t oString();

Using StringBuilder Live Demo

Formatting Strings Using t oString() and String. f ormat()

Method toString() ,[object Object],[object Object],[object Object]

Method String.format() ,[object Object],[object Object],[object Object],String template = "If I were %s, I would %s."; String sentence1 = String.format( template, "developer", "know Java"); System.out.println(sentence1); // If I were developer, I would know Java . String sentence2 = String.format( template, "elephant", "weigh 4500 kg"); System.out.println(sentence2); // If I were elephant, I would weigh 4500 kg.

Formatting Dates ,[object Object],[object Object],[object Object],[object Object],[object Object],Date now = (new GregorianCalendar()).getTime(); System.out.printf("Now is " + "%1$td.%1$tm.%1$tY %1$tH:%1$tM:%1$tS", now ); // Now is 23.05.2006 21:09:32

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object]

Summary (2) ,[object Object],[object Object]

Exercises ,[object Object],[object Object]

Exercises (2) ,[object Object],[object Object],[object Object],We are living in a yellow submarine. We don't have anything else. Inside the submarine is very tight. So we are drinking all the day. We will move out of it in 5 days.

Exercises (3) ,[object Object],[object Object],We are living in a <upcase> yellow submarine</upcase>. We don't have <upcase>anything</upcase> else . We are living in a YELLOW SUBMARINE . We don't have ANYTHING else.

Exercises (4) ,[object Object],[object Object],[protocol]://[server]/[resource]

Exercises (5) ,[object Object],[object Object],[object Object],We are living in a yellow submarine. We don't have anything else. Inside the submarine is very tight. So we are drinking all the day. We will move out of it in 5 days. We are living in a yellow submarine. We will move out of it in 5 days.

Exercises (6) ,[object Object],[object Object],[object Object],Microsoft announced its next generation Java compiler today. It uses advanced parser and special optimizer for the Microsoft JVM. ********* announced its next generation **** compiler today. It uses advanced parser and special optimizer for the ********* ***.

Exercises (7) ,[object Object],[object Object],[object Object]

Exercises (8) ,[object Object],[object Object]

Exercises (9) ,[object Object]

Strings v.1.1

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Strings v.1.1

Editor's Notes