我需要創建程式來為用戶提供生成報告的能力，該報告按鄉鎮名稱的字母順序或鄉鎮平方英里的大小順序顯示。
但是當我使用代碼運行文本檔案時收到錯誤訊息。
如果沒有文本檔案，我的代碼可以作業，但是當我嘗試將文本檔案與代碼一起使用時，我會收到此錯誤。
Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:67)
at java.base/java.lang.Integer.parseInt(Integer.java:678)
at java.base/java.lang.Integer.parseInt(Integer.java:786)
at Main.main(Mice.java:76)
我的代碼：
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
// create mice class
class Mice {
private final double micepopulation;
private final int sizetown;
private final String town;
// =-=-=-=-=-=-=-=-=--==-=
public Mice(double population, int sizetown, String town) {
this.town = town;
this.micepopulation = population;
this.sizetown = sizetown;
}
// --==--=-=-=-=-=-=-=-=-=--=
public String miceelseif() {
if (micepopulation > 75) {
return "Blue";
} else if (micepopulation > 65) {
return "Green";
} else if (micepopulation > 50) {
return "Yellow";
} else if (micepopulation > 35) {
return "Orange";
} else {
return "Red";
}
// -=-=-=-=-=-=-=-=-=-=-=-=-
}
public String getTOWN() {
return town;
}
public String toString() {
return String.format("%-25s%-20.2f%-20d%-20s", town, micepopulation, sizetown, miceelseif());
}
}
public class Main {
public static void main(String[] args) {
int numRecords = getNumRecords();
String[] township = new String[numRecords];
double[] population = new double[numRecords];
int[] townsize = new int[numRecords];
try {
Scanner fileScanner = new Scanner(new File("Micepopulation.txt"));
int index = 0;
while (fileScanner.hasNextLine()) {
township[index] = fileScanner.nextLine();
String[] popTwonSizeContents = fileScanner.nextLine().trim().split("");
population[index] = Double.parseDouble(popTwonSizeContents[0]);
townsize[index] = Integer.parseInt(popTwonSizeContents[1]);
// increment the index
index ;
}
fileScanner.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
Mice[] micePop = new Mice[numRecords];
for (int index = 0; index < micePop.length; index ) {
micePop[index] = new Mice(population[index], townsize[index], township[index]);
}
Scanner scanner = new Scanner(System.in);
int choice;
do {
System.out.println("1: Mice by Town");
System.out.println("2: Mice by size");
System.out.println("3- Town name");
System.out.println("0- Exit");
System.out.print(" Please enter your choice: ");
choice = scanner.nextInt();
scanner.nextLine();
switch (choice) {
case 0 -> System.out.println("thank you, have a good day");
case 1, 2 -> bytown(micePop);
case 3 -> {
System.out.print("please enter town ");
String town = scanner.nextLine();
int foundIndex = townLookUp(micePop, town);
if (foundIndex == -1) {
System.out.println("no town");
} else {
System.out.printf("%-25s%-20s%-20s%-20s\n", "Town", "Mice Population", "Town Size",
"Alerts");
System.out.println(micePop[foundIndex].toString());
}
}
default -> System.out.println("Invalid choice");
}
System.out.println();
} while (choice != 0);
scanner.close();
}
// ==-=-=-===--==-=-=-=-=-=-=-=-=-=--==-
private static void bytown(Mice[] micePop) {
for (int index = 0; index < micePop.length; index ) {
for (int innerIndex = 0; innerIndex < micePop.length - index - 1; innerIndex ) {
if (micePop[innerIndex].getTOWN().compareTo(micePop[innerIndex 1].getTOWN()) > 0) {
Mice temp = micePop[innerIndex];
micePop[innerIndex] = micePop[innerIndex 1];
micePop[innerIndex 1] = temp;
}
}
}
System.out.println("\nREPORT BY TOWN");
printMicePopulation(micePop);
}
// -=-===-=-=-=--==-=-=--==-=-
// =-=--=-==-=-=-=--==-=-=-=-=-=-=--==-=-=--
private static int townLookUp(Mice[] micePop, String township) {
for (int index = 0; index < micePop.length; index ) {
if (micePop[index].getTOWN().equalsIgnoreCase(township)) {
return index;
}
}
return -1;
}
// -=-==-=-=-=--==--==-=-==-=-=-=-=-=-=--==-=-=-----=
private static void printMicePopulation(Mice[] micePop) {
System.out.printf("%-25s%-20s%-20s%-20s\n", "Town", "Mice Population", "Town Size", "Threat Alert");
for (Mice mice : micePop) System.out.println(mice.toString());
}
// -=-==--==--==-==-=-=-===-=-=-=-=-=-=-=-
public static int getNumRecords() {
try {
Scanner scanner = new Scanner(new File("Micepopulation.txt"));
int numRecords = 0;
while (scanner.hasNextLine()) {
numRecords ;
scanner.nextLine();
}
scanner.close();
return numRecords / 2;
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return 0;
}
}
我正在嘗試附加的文本檔案
City of Red
70.81 2137
Boro of Orange
101.77 71
Yellow City
83.13 1034
Green Town
54.79 1819
Blueville
45.71 1514
Indigo Village
4.15 1442
Violeton
119.27 2225
Redburg
7.46 977
Orange Park
16.72 133
Yellow Falls
94.5 4556
Green Haven
326.12 1105242
Blue City
44.69 1979
Indigo Township
113.56 365
Violet Point
35.27 4161
uj5u.com熱心網友回復：
java.lang.NumberFormatException: For input string: ""表示您正在嘗試決議一個不是有效數字的數字。在您的情況下，您正在嘗試將空字串轉換為整數。
您遇到了這個問題，因為人口和townSize數字在您的文本檔案中有一個或多個空格。僅使用split(" ")是不夠的，您將不得不使用split("\\s )來分割一個或多個空格。
Blueville 的號碼有兩個空格，而 Indigo Village 的號碼有一個空格。
轉載請註明出處，本文鏈接：https://www.uj5u.com/net/474719.html
標籤：爪哇
上一篇：模擬物件不能在單元測驗中使用ModelMapper轉換為物體物件
下一篇：NullPointerException：無法呼叫“JComboBox.getSelectedIndex()”，因為“this.this$0.comboBox_1”為空