School class

School.java

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+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import acm.program.ConsoleProgram;
+
+public class School extends ConsoleProgram {
+	ArrayList<String> teachers; 
+	ArrayList<String> subjects;
+	ArrayList<String> students;
+
+	Map<String, ArrayList<String>> teachSubj;
+	Map<String, ArrayList<String>> subjPupils;
+
+	public School() {
+		teachers = new ArrayList<String>();
+		subjects = new ArrayList<String>();
+		students = new ArrayList<String>();
+##
+		teachSubj = new HashMap<>();
+		subjPupils = new HashMap<>();
+	}
+
+	public void addTeacher(String teacher) {
+		teachers.add(teacher);
+		teach.put(teacher, null);
+	}
+
+	public void addSubject(String teacher, String subject) {
+		if (teachers.contains(teacher)) {
+			if (teachSubj.get(teacher) == null) {
+				ArrayList<String> helper = new ArrayList<String>();
+				teachSubj.put(teacher, helper);
+			}
+			if (!teachSubj.get(teacher).contains(subject)) {
+				teachSubj.get(teacher).add(subject);
+			}
+			if (!subjects.contains(subject)) {
+				subjects.add(subject);
+			}
+		}
+	}
+
+	public void addPupil(String pupil, String subject) {
+		if (subjects.contains(subject)) {
+			if (subjPupils.get(subject) == null) {
+				ArrayList<String> helper = new ArrayList<String>();
+				subjPupils.put(subject, helper);
+			}
+
+			subjPupils.get(subject).add(pupil);
+
+			students.add(pupil);
+		}
+	}
+
+	public Iterator<String> getTeachers(String pupil) {
+		if (students.contains(pupil)) {
+			ArrayList<String> result = new ArrayList<String>();
+			for (String teacher : teachSubj.keySet()) {
+				ArrayList<String> subj = teachSubj.get(teacher);
+				if (subj != null) {
+					for (int i = 0; i < subj.size(); i++) {
+						ArrayList<String> pupils = subjPupils.get(subj.get(i));
+						if (pupils != null) {
+							if (pupils.contains(pupil)) {
+								result.add(teacher);
+								break;
+							}
+						}
+					}
+				}
+			}
+			return result.iterator();
+		}
+		return null;
+	}
+
+	public Iterator<String> getPupils(String teacher) {
+		if (teachers.contains(teacher)) {
+			ArrayList<String> result = new ArrayList<String>();
+
+			ArrayList<String> subj = teachSubj.get(teacher);
+			if (subj != null) {
+				for (int i = 0; i < subj.size(); i++) {
+					ArrayList<String> pupils = subjPupils.get(subj.get(i));
+					if(pupils != null){
+						for (int j = 0; j < pupils.size(); j++) {
+							result.add(pupils.get(j));
+						}
+					}
+				}
+			}
+			return result.iterator();
+		}
+		return null;
+	}
+
+	public void removeTeacher(String teacher) {
+		teachers.remove(teachers.indexOf(teacher));
+		teachSubj.remove(teacher);
+	}
+}