我需要一点帮助。我正在尝试缩短我的 main() 并将一些代码移动到方法中并将其放在我的另一个类 Contact.java 中。就像读取文件这样的某些事情，我想要一个方法，它只用于读取文件并将其放入 Contact.java 中。写入文件也是如此，我想要一个可以在 main() 中回调的单独方法。我了解如何制作该方法，但是如何将该方法从 Contact.java 调用回 ContactList.java？有什么建议么？
import java.io.*;
import java.util.*;
public class ContactList {
public static void main(String args[]) throws IOException {
Contact contact;
contact = new Contact();
int action = 0;
ArrayList<Contact> contacts = new ArrayList<Contact>();
while (action != 6) {
System.out.println("\nWelcome to Contact List DB. "
+ "What would you like to do? \n");
System.out.println("1. Enter a new person" + "\n"
+ "2. Print the contact list" + "\n"
+ "3. Retrieve a person's information by last name" + "\n"
+ "4. Retrieve a person's information by email address" + "\n"
+ "5. Retrieve all people who live in a given zip code" + "\n"
+ "6. Exit");
Scanner reader = new Scanner(System.in);
reader.useDelimiter("\n");
action = reader.nextInt();
if (action <= 0 || action > 6) {
System.out.println("Invalid selection. ");
}
switch (action) {
case 1: {
System.out.println("\nEnter Contact Last Name:");
String lastname = reader.next();
if (lastname == null) {
System.out.println("\nInvalid entry. ");
break;
}
else {
contact.setLastName(lastname.toLowerCase());
}
System.out.println("Enter Contact First Name: ");
String firstname = reader.next();
contact.setFirstName(firstname.toLowerCase());
System.out.println("Enter Contact Street Address: ");
String address = reader.next();
contact.setHouseAddress(address.toLowerCase());
System.out.println("Enter Contact City: ");
String city = reader.next();
contact.setCity(city.toLowerCase());
System.out.println("Enter Contact Zip Code: ");
String zip = reader.next();
contact.setZip(zip.toLowerCase());
System.out.println("Enter Contact Email: ");
String email = reader.next();
contact.setEmail(email.toLowerCase());
System.out.println("Enter Contact Phone Number: ");
String phone = reader.next();
contact.setPhone(phone.toLowerCase());
System.out.println("Enter Contact Notes: ");
String notes = reader.next();
contact.setNotes(notes.toLowerCase());
contacts.add(contact);
try {
Contact c = contact;
File file = new File("contactlist.csv");
// If file doesn't exists, then create it.
if (!file.exists()) {
file.createNewFile();
}
try (PrintWriter output = new PrintWriter(new FileWriter(
"contactlist.csv", true))) {
output.printf("%s\r\n", c);
} catch (Exception e) {
}
System.out.println("Your contact has been saved.");
}
catch (IOException e) {
e.printStackTrace();
}
}
break;
case 2: {
int counter = 0;
String line = null;
// Location of file to read
File file = new File("contactlist.csv");
// Sort contacts and print to console
try {
Scanner scanner = new Scanner(file);
// Before printing, add each line to a sorted set. by Seth
// Copeland
Set<String> lines = new TreeSet<>();
while (scanner.hasNextLine()) {
line = scanner.nextLine();
lines.add(line);
counter++;
}
// Print sorted contacts to console.
for (String fileLine : lines) {
String outlook = fileLine.substring(0, 1).toUpperCase()
+ fileLine.substring(1);
System.out.println(outlook);
}
scanner.close();
} catch (FileNotFoundException e) {
}
System.out.println("\n" + counter + " contacts in records.");
}
break;
case 3:
try {
System.out.println("\nEnter the last"
+ "name to search for: ");
String searchterm = reader.next();
// Open the file as a buffered reader
BufferedReader bf = new BufferedReader(new FileReader(
"contactlist.csv"));
// Start a line count and declare a string to hold our
// current line.
int linecount = 0;
String line;
// Let the user know what we are searching for
System.out.println("Searching for " + searchterm
+ " in file...");
// Loop through each line, putting the line into our line
// variable.
boolean noMatches = true;
while ((line = bf.readLine()) != null) {
// Increment the count and find the index of the word.
linecount++;
int indexfound = line.indexOf(searchterm.toLowerCase());
// If greater than -1, means we found a match.
if (indexfound > -1) {
System.out.println("\nContact was FOUND\n"
+ "\nContact " + linecount + ": " + line);
noMatches = false;
}
}
// Close the file after done searching
bf.close();
if (noMatches) {
System.out.println("\nNO MATCH FOUND.\n");
}
}
catch (IOException e) {
System.out.println("IO Error Occurred: " + e.toString());
}
break;
case 4:
try {
System.out.println("\nEnter the email "
+ "address to search for: ");
String searchterm = reader.next();
// Open the file as a buffered reader
BufferedReader bf = new BufferedReader(new FileReader(
"contactlist.csv"));
// Start a line count and declare a string to hold our
// current line.
int linecount = 0;
String line;
// Let the user know what we are searching for
System.out.println("\nSearching for " + searchterm
+ " in file...");
// Loop through each line, put the line into our line
// variable.
boolean noMatches = true;
while ((line = bf.readLine()) != null) {
// Increment the count and find the index of the word
linecount++;
int indexfound = line.indexOf(searchterm.toLowerCase());
// If greater than -1, means we found a match
if (indexfound > -1) {
System.out.println("\nContact was FOUND\n"
+ "\nContact " + linecount + ": " + line);
noMatches = false;
}
}
// Close the file after done searching
bf.close();
if (noMatches) {
System.out.println("\nNO MATCH FOUND.\n");
}
}
catch (IOException e) {
System.out.println("IO Error Occurred: " + e.toString());
}
break;
case 5:
try {
System.out.println("\nEnter the Zipcode to search for: ");
String searchterm = reader.next();
// Open the file as a buffered reader
BufferedReader bf = new BufferedReader(new FileReader(
"contactlist.csv"));
// Start a line count and declare a string to hold our
// current line.
int linecount = 0;
String line;
// Let the user know what we are searching for
System.out.println("\nSearching for " + searchterm
+ " in file...");
// Loop through each line, stashing the line into our line
// variable.
boolean noMatches = true;
while ((line = bf.readLine()) != null) {
// Increment the count and find the index of the word.
linecount++;
int indexfound = line.indexOf(searchterm.toLowerCase());
// If greater than -1, means we found a match.
if (indexfound > -1) {
System.out.println("\nContact was FOUND\n"
+ "\nContact " + linecount + ": " + line);
noMatches = false;
}
}
// Close the file after done searching
bf.close();
if (noMatches) {
System.out.println("\nNO MATCH FOUND.\n");
}
}
catch (IOException e) {
System.out.println("IO Error Occurred: " + e.toString());
}
break;
}
}
}
}