I've been learning Java for a month now using programmingbydoing.com in addition with reading the Java reference. I've had very very basic programming experience and I'm trying to improve my skills. These assignments are my first large projects that I've attempted.
I attempted an address book twice. The first time I was unhappy with my code. It was extremely messy and confusing. The second time I used comments and managed to complete it, but it's definitely still awkward.
import java.util.Scanner;
class Book{
Scanner s = new Scanner(System.in);
//Nested class for each entry
class Entry{
private String first;
private String last;
private String address;
private String email;
Entry(String first, String last, String address, String email){
this.first = first;
this.last = last;
this.address = address;
this.email = email;
}
Entry(){
first = "";
last = "";
address = "";
email = "";
}
public void readEntry(){
System.out.println("First Name:"+first );
System.out.println("Last Name:"+last );
System.out.println("Address:"+address );
System.out.println("Email:"+email );
}
}
//Keeps track of how many entries are in the book
private int entries = 0;
Entry[] contents;
public void initEntries(int e){
contents = new Entry[e];
for (int i = 0;i<contents.length;i++){ //Initializes an array of entries, then loops through to initialize each individual entry
contents[i] = new Entry();
}
}
public int getEntries(){
return contents.length;
}
//Adds an entry to the book
public void add(String first, String last, String address, String email){
if (entries<contents.length){
contents[entries] = new Entry(first, last, address, email);
entries++;
}
else System.out.println("Error: book is full");
}
//Removes an entry from the book
public void remove(int entry){
if (entries>0){
contents[entry] = new Entry();
for (int i = 0;i<entries-entry;i++){
if (entry+1==entries) contents[entry] = new Entry();
else{
Entry temp = contents[entry+i];
contents[entry+i] = contents[entry+i+1]; //Removes an entry end moves each entry after it one backwards.
contents[entry+i+1] = temp;
}
}
entries--;
}
else System.out.println("Error: book is empty.");
}
//Changes the values of an entry
public void edit(String first, String last, String address, String email, int selection){
contents[selection].first = first;
contents[selection].last = last;
contents[selection].address = address;
contents[selection].email = email;
}
//Sorts the book based on a part of the entry
//int n is used to tell which part of the entries to base the sort on
public void sort(int n){
for(int i = 0;i<contents.length;i++){
for (int j = 0;j<contents.length;j++){
switch(n){
case 1:
if (contents[i].first.compareTo(contents[j].first)<0){
Entry temp = contents[i];
contents[i] = contents[j];
contents[j] = temp;
}
break;
case 2:
if (contents[i].last.compareTo(contents[j].last)<0){
Entry temp = contents[i];
contents[i] = contents[j];
contents[j] = temp;
}
break;
case 3:
if (contents[i].address.compareTo(contents[j].address)<0){
Entry temp = contents[i];
contents[i] = contents[j];
contents[j] = temp;
}
break;
case 4:
if (contents[i].email.compareTo(contents[j].email)<0){
Entry temp = contents[i];
contents[i] = contents[j];
contents[j] = temp;
}
break;
default:
System.out.println("Error: invalid field");
break;
}
}
}
}
public void addFromCopy(Entry e){
if (entries<contents.length){
contents[entries] = e;
entries++;
}
else System.out.println("Error: book is full");
}
}
AddressBook2
public class AddressBook2 {
public static void main(String[] args){
Scanner s = new Scanner(System.in);
System.out.print("How many books do you want to create? ");
int howManyBooks;
int howManyEntries;
Book[] library = new Book[0];
while(true){
howManyBooks = s.nextInt();
if (howManyBooks>0){
library = new Book[howManyBooks]; //This code decides how many books are in the array of books/the library
break;
}
else System.out.print("You must create at least 1 book.");
}
for (int i=0;i<library.length;i++){
library[i] = new Book(); //Fixed reference to null because each book in the library had not been initialized yet.
while(true){
System.out.print("How many entries in book "+i+"? ");
howManyEntries = s.nextInt();
if (howManyEntries>0) {
library[i].initEntries(howManyEntries); //This code decides how many entries are in each book in the library
break;
}
else System.out.println("You must create at least 1 Entry.");
}
}
boolean done = false;
int selectedBook = 0;
int selection;
while (done==false){
System.out.println("Book "+selectedBook+" is currently selected.");
for (int i = 0;i<library[selectedBook].getEntries();i++){
System.out.println("===========Entry "+i+" ===========");
library[selectedBook].contents[i].readEntry(); //Accessing the array of entries INSIDE the array of books/the library
System.out.println("================================");
}
System.out.println("Select an option!");
System.out.println("1. Add an entry");
System.out.println("2. Remove an entry");
System.out.println("3. Edit an entry");
System.out.println("4. Sort all entries in this book");
System.out.println("5. Select another book");
System.out.println("6. Move entry across books");
System.out.println("7. Exit the menu");
System.out.print("> ");
selection = s.nextInt();
String first, last, address, email;
switch(selection){
case 1:
System.out.print("First name? ");
first = s.next();
System.out.print("Last name? ");
last = s.next();
System.out.print("Address? ");
address = s.next();
System.out.print("Email? ");
email = s.next();
library[selectedBook].add(first, last, address, email);
break;
case 2:
System.out.print("Remove which entry? ");
int entry = s.nextInt();
library[selectedBook].remove(entry);
break;
case 3:
System.out.print("Edit which entry?");
int whichEntry = s.nextInt();
System.out.print("First name? ");
first = s.next();
System.out.print("Last name? ");
last = s.next();
System.out.print("Address? ");
address = s.next();
System.out.print("Email? ");
email = s.next();
library[selectedBook].edit(first, last, address, email, whichEntry);
break;
case 4:
System.out.println("Sort alphabetically by which field?");
System.out.println("1. Sort by first name");
System.out.println("2. Sort by last name");
System.out.println("3. Sort by address");
System.out.println("4. Sort by email");
library[selectedBook].sort(s.nextInt());
break;
case 5:
System.out.print("Select which book?");
selectedBook = s.nextInt();
break;
case 6:
System.out.print("Move which entry? ");
int entryNo = s.nextInt();
Book.Entry entryToMove = library[selectedBook].contents[entryNo];
library[selectedBook].remove(entryNo);
System.out.print("To which book? ");
int whichBook = s.nextInt();
library[whichBook].addFromCopy(entryToMove);
break;
case 7:
done = true;
break;
default:
System.out.print("Please choose a valid menu number");
}
}
}
}
