[英]java.util.NoSuchElementException from Scanner
我的掃描儀正在讀取文件時遇到問題。 當有逗號后跟空格或創建新行時,假設創建一個新標記,但是在4個標記之后,它會拋出NoSuchElementException。
private Map<String, Double> createElementMassMap(String filePath) {
Map<String, Double> elementMap = new HashMap<>();
try (Scanner sc = new Scanner(new FileReader(filePath))) {
sc.useDelimiter(Pattern.compile("(, ) | (\r\n)"));
sc.useLocale(Locale.US);
while(sc.hasNext()) {
String name = sc.next();
System.out.println(name);
double mass = sc.nextDouble();
System.out.println(mass);
elementMap.put(name, mass);
}
} catch (IOException e) {
e.printStackTrace();
JOptionPane.showMessageDialog(self, "Error loading ElementMasses file.", "IOException", JOptionPane.ERROR_MESSAGE);
}
return elementMap;
}
這是它試圖閱讀的文件
H, 1.00
O, 16.00
我確保文件中沒有空行。
我是一個白痴,我的模式搞砸了。
//instead of
sc.useDelimiter(Pattern.compile("(, ) | (\r\n)"));
//it should be this
sc.useDelimiter(Pattern.compile("(, )|(\r\n)"));
謝謝你們有用的答案!
你在用什么平台? 行分隔符因平台而異。 使用它來支持兩者(當然刪除正則表達式中'|'周圍的額外空格)。
sc.useDelimiter("(, )|(\r\n)|(\n)");
我嘗試在我的計算機上運行此代碼,如下所示:
import javax.swing.JOptionPane;
import java.util.Scanner;
import java.util.Locale;
import java.util.regex.Pattern;
import java.io.FileReader;
import java.util.HashMap;
import java.util.Map;
import java.io.IOException;
import java.awt.Component;
public class Test {
public static void main(String[] args) {
createElementMassMap("file.txt");
}
private static Map<String, Double> createElementMassMap(String filePath) {
Map<String, Double> elementMap = new HashMap<>();
try (Scanner sc = new Scanner(new FileReader(filePath))) {
sc.useDelimiter(Pattern.compile("(, ) | (\r\n) | (\n)"));
sc.useLocale(Locale.US);
while(sc.hasNext()) {
String name = sc.next();
System.out.println(name);
System.out.println("hi");
double mass = sc.nextDouble();
System.out.println(mass);
elementMap.put(name, mass);
}
} catch (IOException e) {
e.printStackTrace();
JOptionPane.showMessageDialog((Component)new Object(), "Error loading ElementMasses file.", "IOException", JOptionPane.ERROR_MESSAGE);
}
return elementMap;
}
}
而我得到的是
H, 1.00
O, 16.00
hi
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextDouble(Scanner.java:2413)
at Test.createElementMassMap(Test.java:25)
at Test.main(Test.java:13)
所以,看起來第一場比賽與整個文件相匹配。 如果刪除管道周圍的空格:
import javax.swing.JOptionPane;
import java.util.Scanner;
import java.util.Locale;
import java.util.regex.Pattern;
import java.io.FileReader;
import java.util.HashMap;
import java.util.Map;
import java.io.IOException;
import java.awt.Component;
public class Test {
public static void main(String[] args) {
createElementMassMap("file.txt");
}
private static Map<String, Double> createElementMassMap(String filePath) {
Map<String, Double> elementMap = new HashMap<>();
try (Scanner sc = new Scanner(new FileReader(filePath))) {
sc.useDelimiter(Pattern.compile("(, ) | (\r\n) | (\n)"));
sc.useLocale(Locale.US);
while(sc.hasNext()) {
String name = sc.next();
System.out.println(name);
System.out.println("hi");
double mass = sc.nextDouble();
System.out.println(mass);
elementMap.put(name, mass);
}
} catch (IOException e) {
e.printStackTrace();
JOptionPane.showMessageDialog((Component)new Object(), "Error loading ElementMasses file.", "IOException", JOptionPane.ERROR_MESSAGE);
}
return elementMap;
}
}
消息消失,完美無缺
我不喜歡掃描儀,盡可能多地使用掃描儀。 如果你想嘗試bufferedReader,這是做到這一點的方法:
BufferedReader in = new BufferedReader(new FileReader(filePath));
StringTokenizer st;
String line;
try {
while((line = in.readLine()) != null) {
st = new StringTokenizer(line,", " );
String name = st.nextToken();
System.out.println(name);
double mass = Double.parseDouble(st.nextToken());
System.out.println(mass);
}
} catch (Exception e) {
// kaboom... something happened
e.printStackTrace();
}
編輯:您可以在StringTokenizer構造函數中調整分隔符以滿足您的需要
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.