我正在尝试使用输入,但是我遇到了麻烦……如果我使用下面的代码,它还没有结束……所以我陷入了无限循环。即使我输入的文件结尾,它也会这样写:
...
A number has not been parsed from line n
A number has not been parsed from line n+1
A number has not been parsed from line n+2
... (infinite)
但是我想代替这个:
...
End of input detected!
输入看起来像这样:
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double[] numbers = new double[10];
int counter_number = 0;
while (sc.hasNextLine()) {
...
line++;
if(sc.hasNextDouble()) {
numbers[counter_number] = sc.nextDouble();
counter_number++;
}
else{
System.out.println("A number has not been parsed from line "+ line);
continue;
}
if (sc.hasNextLine() == false) {
System.err.println("End of input detected!");
}
if (((counter_number)==10) || ((sc.hasNextLine() == false)
...
counter_number = 0;
}
}
这个循环永远不会结束吗?我看到了他们在其中使用“ while(sc.hasNextLine())”的教程,并且教程完成了。我是Java的初学者。
答案 0 :(得分:0)
您执行的唯一执行读取器的操作是sc.nextDouble()
,但这仅在sc.hasNextDouble()
返回true的情况下发生。这意味着如果您的代码遇到非双输入,它将永远被卡住
作为一般说明-sc.hasNextLine() == false
应替换为!sc.hasNextLine()
答案 1 :(得分:0)
static Scanner sc = new Scanner(System.in);
public static void main(String[] args) {
double[] numbers = new double[10];
int counter_number = 0;
int line = 0;
while (sc.hasNextLine()){
line++;
String thisLine = sc.nextLine();
// this is what i wrote.
if(thisLine.trim().isEmpty()) {
// if the line is empty, will exit the loop.
System.out.println("lines: "+line); // lines
System.out.println("End of input detected!"); // end.
break;
}
try {
// if the input is a double
numbers[counter_number] = Double.parseDouble(thisLine);
counter_number++;
} catch (NumberFormatException e) {
// if not
System.out.println("A number has not been parsed from line "+ line);
continue;
}
// idk
if (counter_number == numbers.length) {
counter_number = 0;
}
};
}
FIX。我不会关闭扫描仪,并且...您可以尝试使用此功能。当我输入空行时,此代码结束。