{small lecturenumber - hepage :} Introduction{small lecturenumber - hepage :} Strings in Java{small lecturenumber - hepage :} Overloaded operators{small lecturenumber - hepage :} Strings are immutable{small lecturenumber - hepage :} Iterating over strings{small lecturenumber - hepage :} String practice{small lecturenumber - hepage :} String equality{small lecturenumber - hepage :} String practice{small lecturenumber - hepage :} Using Scanner to read from files{small lecturenumber - hepage :} String practice{small lecturenumber - hepage :} Building Project 1Intro to Programming IIStrings and FilesChris BrooksDepartment of Computer ScienceUniversity of San FranciscoDepartment of Computer Science — University of San Francisco – p. 1/??6-2: Introduction•In project 1, you’ll be working extensively with strings.◦If you do the extra credit, you’ll also be working with files.•Therefore, it’s useful to take a bit of time to remember how towork with strings.Department of Computer Science — University of San Francisco – p. 2/??6-3: Strings in Java•Strings in Java are objects•This mean that they have a set of methods they respond to:◦compareTo(), equals()◦indexOf()◦length()◦replace()◦startsWith(), endsWith()◦etcDepartment of Computer Science — University of San Francisco6-4: Overloaded operators•We can also use the ’+’ symbol to concatenate strings.◦String s1 = “hello”◦String s2 = “world”◦String s3 = s1 + s2 // s3 = “hello world”•This is a phenomenon called overloading; an operator isredifined to provide different functionality.Department of Computer Science — University of San Francisco – p. 4/??6-5: Strings are immutable•Strings are immutable◦This means that once a string is created, it can’t bechanged.◦To change it, you need to create a copy.•String s1 = “hello world”•To change “hello” to “goodbye”, we’d need to do:•String s2 = s1.replace(“hello”, “goodbye”);•s2 is “goodbye world”, s1 is unchangedDepartment of Computer Science — University of San Francisco – p. 5/??6-6: Iterating over strings•To find the character at a particular location, use charAt(intindex)String s1 = ‘‘I love Java’’for (int i = 0; i < s1.length(); i++) {System.out.println(s1.charAt(i));}Department of Computer Science — University of San Francisco6-7: String practice•Write a program that:◦Reads in a string from System.in◦Iterates over the string and prints out all the vowels.Department of Computer Science — University of San Francisco – p. 7/??6-8: String equality•To test whether two strings have the same contents, useequals() or equalsIgnoreCase();•== will test for object equality◦String s1 = “foo”;◦String s2 = “foo”;◦s1.equals(s2), but not s1 == s2•You can also use compareTo()◦Returns -1 if s1 comes before s2, 0 if they’re equal, and 1 ifs1 comes after s2.Department of Computer Science — University of San Francisco – p. 8/??6-9: String practice•Write a program that will:◦Read a string in from System.in;◦Print out the first word in the string.Department of Computer Science — University of San Francisco6-10: Using Scanner to read from files•We can use the Scanner class to read from a file instead ofSystem.intry {Scanner sc = new Scanner(new File("studentlist"));while (sc.hasNext()) {System.out.println(sc.next());}} catch(FileNotFoundException e) {System.out.println("File not found.");}Department of Computer Science — University of San Francisco – p. 10/??6-11: String practice•Read in the file “studentfile” and print out all names beginningwith ’a’.•Read in the file ’studentfile’ and print out all people with firstnames of longer than 5 letters.•Read in the file ’studentfile’ and print out all people whose Lastname comes after ’jones’ in the alphabet.Department of Computer Science — University of San Francisco – p. 11/??6-12: Building Project 1•The first class to consider is the Token class.•Two instance variables:◦type◦value•class variables for each type•setters and getters•toString(), plus a unit test.Department of Computer Science — University of San
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