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75 lines
2.2 KiB
75 lines
2.2 KiB
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import java.util.List;
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import java.util.HashSet;
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import java.util.Set;
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/*
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* SD2x Homework #10
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* Modify the method below so that it uses defensive programming.
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* Please be sure not to change the method signature!
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*/
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public class FriendFinder {
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protected ClassesDataSource classesDataSource;
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protected StudentsDataSource studentsDataSource;
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public FriendFinder(ClassesDataSource cds, StudentsDataSource sds) {
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classesDataSource = cds;
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studentsDataSource = sds;
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}
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public Set<String> findClassmates(Student theStudent) {
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if(theStudent == null) throw new IllegalArgumentException();
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if(theStudent.getName() == null) throw new IllegalArgumentException();
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if(this.classesDataSource == null) throw new IllegalStateException();
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if(this.studentsDataSource== null) throw new IllegalStateException();
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String name = theStudent.getName();
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if (name == null) throw new IllegalStateException();
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// find the classes that this student is taking
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List<String> myClasses = classesDataSource.getClasses(name);
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if (myClasses == null) return null;
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Set<String> classmates = new HashSet<String>();
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// use the classes to find the names of the students
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for (String myClass : myClasses) {
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// list all the students in the class
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if(myClass == null) continue;
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List<Student> students = studentsDataSource.getStudents(myClass);
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if (students == null) continue;
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for (Student student : students) {
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if (student == null) continue;
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if(student.getName() == null) continue;
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// find the other classes that they're taking
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List<String> theirClasses = classesDataSource.getClasses(student.getName());
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if (theirClasses == null) continue;
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// see if all of the classes that they're taking are the same as the ones this student is taking
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boolean same = true;
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for (String c : myClasses) {
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if (c == null) continue;
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if (theirClasses.contains(c) == false) {
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same = false;
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break;
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}
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}
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if (same) {
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if (student.getName().equals(name) == false && classmates.contains(student.getName()) == false)
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classmates.add(student.getName());
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}
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}
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}
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if (classmates.isEmpty()) {
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return null;
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}
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else return classmates;
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}
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}
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