我是編碼新手，正在嘗試學習 JAVA，并使用不同的方法來完成簡單的任務。我想制作一個簡單的通訊錄，具有“添加聯系人、按號碼搜索、按姓名搜索等”功能。我的大多數方法都有效，但以下兩種方法有問題。當我調用時modify Contact，即使我嘗試替換名稱，代碼也會在文件中創建一個新行。然后我調用delete By Name刪除未修改的行，并且收到以下錯誤。（我知道錯誤的原因，但我找不到有效的解決方案......） public static void modifyContact(String namee){ Scanner sca =new Scanner(System.in); String newName = sca.nextLine(); try { String[] s; boolean foundPerson = false; Scanner sc = new Scanner(new File("addressBook.txt")); while (sc.hasNextLine()) { s = sc.nextLine().split(","); if (s[0].equals(namee)) { s[0]=s[0].replace(s[0],newName); System.out.println("Name is " + namee + " phone number is " + s[1] + " ,address is " + s[3] + " and email is " + s[2]); foundPerson = true; deleteByName(namee); File file =new File("addressBook.txt"); FileWriter pw = new FileWriter(file,true); pw.write(s[0]+","+s[1]+","+s[2]+","+s[3]); pw.close(); } } sc.close(); deleteByName(namee); if (!foundPerson) { System.out.println("No contact found with " + namee); } } catch (IOException ex) { //System.out.println(ex.getMessage()); } } public static void deleteByName(String na){ try{ File inputFile = new File("addressBook.txt"); // Your file File tempFile = new File("TempFile.txt");// temp file BufferedReader reader = new BufferedReader(new FileReader(inputFile)); BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile)); String currentLine; while((currentLine = reader.readLine()) != null) { if(currentLine.contains(na)) continue; writer.write(currentLine); writer.newLine(); }
5 回答
三國紛爭
TA貢獻1804條經驗 獲得超7個贊
有兩種解決方案：
不要關閉掃描儀。保持其打開狀態，直到不需要為止。換句話說，在循環之后關閉它。
通過調用 重新創建掃描儀
sc = new Scanner(new File("addressBook.txt"));。但是，由于這將創建一個新的掃描儀，因此它將再次從第一行開始讀取。
12345678_0001
TA貢獻1802條經驗 獲得超5個贊
您的主要問題是您deleteByName()在循環內調用刪除原始文件然后重用Scanner.
你應該這樣做：
找到所有
name呼叫
deleteByName()與所有發現names。
public final class AddressBookManager {
private final File file;
public AddressBookManager(File file) {
this.file = file;
}
public void modifyContact(String oldName, String newName) throws IOException {
if (isContactExists(oldName))
updateContactName(oldName, newName);
}
private boolean isContactExists(String name) throws FileNotFoundException {
try (Scanner scan = new Scanner(file)) {
while (scan.hasNextLine()) {
String str = scan.nextLine();
if (str.startsWith(name + ',')) {
String[] parts = str.split(",");
System.out.format("Contact found. Name '%s', phone number '%s', address '%s', email '%s'\n", parts[0], parts[1], parts[2],
parts[3]);
return true;
}
}
System.out.println("No contact found with name '" + name + '\'');
return false;
}
}
private void updateContactName(String curName, String newName) throws IOException {
File tmp = new File(file.getParent(), "TempFile.txt");
try (BufferedReader in = new BufferedReader(new FileReader(file));
BufferedWriter out = new BufferedWriter(new FileWriter(tmp))) {
String str;
while ((str = in.readLine()) != null) {
if (str.startsWith(curName))
str = newName + str.substring(str.indexOf(','));
out.write(str);
out.newLine();
}
}
System.out.println("remove old file: " + file.delete());
System.out.println("rename temp file: " + tmp.renameTo(file));
}
public static void main(String... args) throws IOException {
AddressBookManager addressBookManager = new AddressBookManager(new File("d:/addressBook.txt"));
String curName = "oleg";
String newName = getNewName(curName);
addressBookManager.modifyContact(curName, newName);
}
private static String getNewName(String curName) {
try (Scanner scan = new Scanner(System.in)) {
System.out.print("Enter new name for (" + curName + "): ");
return scan.nextLine();
}
}
}
海綿寶寶撒
TA貢獻1809條經驗 獲得超8個贊
問題是當您使用系統關閉掃描儀時。來自系統的輸入流也被關閉。因此，即使您使用 System.in 創建一個新的掃描儀，您也將無法重用該掃描儀。如果您使用的是 java 7，您可以使用 try 和資源來通過 Java 本身關閉所有 autocCleasable 資源。這將解決該問題。
public static void modifyContact(String namee) {
File file = new File("addressBook.txt");
try (Scanner sca = new Scanner(System.in);
Scanner sc = new Scanner(file);
FileWriter pw = new FileWriter(file, true);) {
String[] s;
boolean foundPerson = false;
String newName = sca.nextLine();
while (sc.hasNextLine()) {
s = sc.nextLine().split(",");
if (s[0].equals(namee)) {
s[0] = s[0].replace(s[0], newName);
System.out.println("Name is " + namee + " phone number is " + s[1] + " ,address is " + s[3]
+ " and email is " + s[2]);
foundPerson = true;
deleteByName(namee);
pw.write(s[0] + "," + s[1] + "," + s[2] + "," + s[3]);
}
}
if (!foundPerson) {
System.out.println("No contact found with " + namee);
}
} catch (IOException ex) {
// System.out.println(ex.getMessage());
}
}
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