我需要我的程序检测其联系人列表中的先前条目，并禁止用户输入两个相同的条目。我一直在尝试，但是我要么允许所有条目，要么无效的条目仍保存到我的列表中。
我想要做的是使它的程序成为电话簿，并且现实生活中没有两个人应该有相同的电话号码。这就是为什么我希望只有给定号码的一个联系人。
这是我检查条目的代码：
System.out.print("Enter Number: ");
number = stdin.nextLine(); // read the number
while(!number.matches(pattern)) { // as long as user doesnt enters correct format, loop
System.out.println("Error!");
System.out.println("Not proper digit format! Use \"012-3456\", \"(012)345-6789\"" +
", or \"012-345-6789\" format.");
System.out.print("Enter number: ");
number = stdin.nextLine();
}
for (Entry e : contactList) {
if (e.number.equals(number)) {
System.out.println("This phone number already exist. Please check contacts.");
System.out.println("");
return;
}else{
break;
}
}
contactList[num_entries].number = number;
这是我的完整代码供参考：
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;
import java.util.Scanner;
class Entry {
public String fname, lname, number, note;
}
class PBN {
public static Entry[] contactList;
public static int num_entries;
public static Scanner stdin = new Scanner(System.in);
public static void main(String args[]) throws Exception{
Scanner s = new Scanner(System.in);
int i;
char C;
String code, Command;
contactList = new Entry[999];
num_entries = 0;
try {
readPhoneBook("PhoneBook.txt");
} catch (FileNotFoundException e) {}
System.out.println("Codes are entered as 1 to 8 characters.\n" +
"Use Commands:\n" +
" \"e\" for enter a new contact,\n" +
" \"f\" for find contact by fist name,\n" +
" \"r\" for find contact by last name,\n" +
" \"y\" for find contact by phone number,\n" +
" \"l\" for listing all the existing contacts,\n" +
" \"d\" for removing contacts by phone number,\n" +
" \"a\" for sort alphabetically by first name,\n" +
" \"n\" for sort alphabetically by last name,\n" +
" \"p\" for sort by number,\n" +
" \"q\" to quit.");
Command = null;
C = ' ';
while(true) { // loop infinitely
System.out.print("Command: ");
Command = stdin.nextLine();
C = Command.charAt(0);
switch (C) {
case 'e': addContact(); break;
case 'f':
System.out.print("Search for contact by first name: ");
code = stdin.next();
stdin.nextLine();
index(code); break;
case 'r':
System.out.print("Search for contact by last name: ");
code = stdin.next();
stdin.nextLine();
index1(code); break;
case 'y':
System.out.print("Search for contact by phone number: ");
code = stdin.next();
stdin.nextLine();
index2(code); break;
case 'l':
listAllContacts(); break;
case 'q': // when user wants to quit
CopyPhoneBookToFile("PhoneBook.txt");
System.out.println("Quitting the application. All the entries are "
+ "stored in the file PhoneBook1.txt");
System.exit(0); // simply terminate the execution
case 'a':
sortList1();
break;
case 'n':
sortList2();
break;
case 'p':
sortListByPhoneNumber();
break;
case 'd': // m for deleting a contact; delete by phone number
System.out.print("Enter the phone number of a contact you wish to delete : ");
String number = stdin.nextLine();// read the contact number
removeEntry1(number); // remove the number from the entries
break;
default:
System.out.println("Invalid command Please enter the command again!!!");
}
}
}
public static void readPhoneBook(String FileName) throws Exception {
File F;
F = new File(FileName);
Scanner S = new Scanner(F);
while (S.hasNextLine()) {
contactList[num_entries]= new Entry();
contactList[num_entries].fname = S.next();
contactList[num_entries].lname = S.next();
contactList[num_entries].number = S.next();
contactList[num_entries].note = S.nextLine();
num_entries++;
}
S.close();
}
public static void addContact() {
System.out.print("Enter first name: ");
String fname = stdin.nextLine();
String lname;
String number;
String pattern = "^\\(?(\\d{3})?\\)?[- ]?(\\d{3})[- ](\\d{4})$";
while (fname.length() > 8 || fname.length() < 1) {
System.out.println("First name must be between 1 to 8 characters.");
System.out.print("Enter first name: ");
fname = stdin.nextLine();
}
contactList[num_entries] = new Entry();
contactList[num_entries].fname = fname;
System.out.print("Enter last name: ");
lname = stdin.nextLine();
while (lname.length() > 8 || lname.length() < 1) {
System.out.println("First name must be between 1 to 8 characters.");
System.out.print("Enter first name: ");
lname = stdin.nextLine();
}
contactList[num_entries].lname = lname;
System.out.print("Enter Number: ");
number = stdin.nextLine(); // read the number
while(!number.matches(pattern)) { // as long as user doesnt enters correct format, loop
System.out.println("Error!");
System.out.println("Not proper digit format! Use \"012-3456\", \"(012)345-6789\"" +
", or \"012-345-6789\" format.");
System.out.print("Enter number: ");
number = stdin.nextLine();
for (Entry e : contactList) {
if (e.number.equals(number)) {
System.out.println("This phone number already exist. Please check contacts.");
System.out.println("");
break;
} else {
return;
}
}
}
contactList[num_entries].number = number;
System.out.print("Enter Notes: ");
contactList[num_entries].note = stdin.nextLine();
num_entries++;
System.out.println();
}
public static void listAllContacts() {
for(Entry e : contactList) {
if(e != null)
displayContact(e);
else
break;
}
}
public static int index(String Key) {
// Function to get the index of a key from an array
// if not found, returns -1
for (int i=0; i < num_entries; i++) {
if (contactList[i].fname.equalsIgnoreCase(Key)) {
if (i >= 0) displayContact(contactList[i]);
//return i;
} // Found the Key, return index.
}
return -1;
}
public static int index1(String Key) {
// Function to get the index of a key from an array
// if not found, returns -1
for (int i=0; i < num_entries; i++) {
if (contactList[i].lname.equalsIgnoreCase(Key)) {
if (i >= 0) displayContact(contactList[i]);
//return i;
} // Found the Key, return index.
}
return -1;
}
public static int index2(String Key) {
// Function to get the index of a key from an array
// if not found, returns -1
for (int i=0; i < num_entries; i++) {
if (contactList[i].number.equalsIgnoreCase(Key)) {
if (i >= 0) displayContact(contactList[i]);
//return i;
} // Found the Key, return index.
}
return -1;
}
public static void displayContact(Entry contact) {
System.out.println("--"+ contact.fname+"\t");
System.out.println("--"+ contact.lname+"\t");
System.out.println("--"+ contact.number+"\t");
System.out.println("--"+ contact.note);
System.out.println("");
}
public static void sortList1() {
int i;
Entry temp;
temp = new Entry();
for (int j = 0; j< num_entries; j++) {
for (i = j + 1; i < num_entries; i++) {
if (contactList[j].fname.compareToIgnoreCase(contactList[i].fname)> 0) {
temp = contactList[j];
contactList[j] = contactList[i];
contactList[i] = temp;
}
}
}listAllContacts();
}
public static void sortList2() {
int i;
Entry temp;
temp = new Entry();
for (int j = 0; j< num_entries; j++) {
for (i = j + 1; i < num_entries; i++) {
if (contactList[j].lname.compareToIgnoreCase(contactList[i].lname)> 0) {
temp = contactList[j];
contactList[j] = contactList[i];
contactList[i] = temp;
}
}
}listAllContacts();
}
public static void CopyPhoneBookToFile(String FileName) throws Exception{
FileOutputStream out = new FileOutputStream(FileName);
PrintStream P = new PrintStream( out );
for (int i=0; i < num_entries; i++) {
P.println(
contactList[i].fname + "\t" +
contactList[i].lname + "\t" +
contactList[i].number + "\t" +
contactList[i].note);
}
}
public static void removeEntry1(String number) {
Entry[] newcontactList = new Entry[contactList.length];
int i = 0;
for(Entry e : contactList) {
if(e == null) break; // if an entry is null then break the loop
if(e.number.equals(number)) // if the given number matches the current number
continue; // then skip
newcontactList[i++] = e;
}
num_entries--; // decrease the number of entries by 1;
contactList = newcontactList;
}
public static void sortListByPhoneNumber() {
int i;
Entry temp;
for (int j = 0; j < num_entries; j++) {
for (i = j + 1; i < num_entries; i++) {
if (contactList[j].number.compareToIgnoreCase(contactList[i].number) > 0) {
temp = contactList[j];
contactList[j] = contactList[i];
contactList[i] = temp;
}
}
}
listAllContacts();
}
}
最佳答案
问题是，当您遍历for (Entry e : contactList)中的contactList时，您并未检查整个列表！
例如。如果在第一个循环中e.number不等于新数字，则转到else语句并中断循环，然后转到contactList[num_entries].number = number;并保存可能已经存在的数字；
要以最少的更改来修复代码-只需删除else{ break;}
如果您想要一个更安全，更高效的解决方案，请对contactList使用HashSet数据结构，或者如果希望对其进行排序，请使用TreeSet-这将确保您永远不会有重复的条目，可以使用Set.contains （数字）来检查条目是否已经存在，另外，HashSet会提高对O（1）的条目查找的复杂性，TreeSet会使O（logn）稍差-要么更好，然后遍历整个数组（即O（n））。