java - 从java中的文本文件填充二维数组(抛出NoSuchElementExcecption)
问题描述
我正在尝试从文本文件中填充一个二维数组(它只是 pi 到小数点后 900 位,除了 3.14 之外没有空格或其他任何东西......)现在它将打印我所在的行和列索引,以及计数器(最终将被删除)。
import java.util.Scanner;
public class Array {
public static void main(String[] args) throws Exception {
// instantiate input file
java.io.File file = new java.io.File("C:\\arrayinput.txt");
// instantiate scanner to read file
Scanner scanner = new Scanner(file);
// instantiate array
String[][] array = new String[20][45];
// instantiate counter
int i = 1;
// loop to read file and assign a character to each array element
for (int rows = 0; rows < array.length; rows++) {
for (int columns = 0; columns < array[rows].length; columns++) {
System.out.println("Row: " + rows + ", column: " + columns + ", counter = " + i);
i++;
array[rows][columns] = scanner.next();
} // end inner for loop
} // end outer for loop
scanner.close();
}// end main method
}
此代码将循环两次并显示:
行:0,列:0,计数器 = 1
行:0,列:1,计数器 = 2
线程“主”java.util.NoSuchElementException 中的异常
at java.util.Scanner.throwFor(Unknown Source) at java.util.Scanner.next(Unknown Source) at Array.main(Array.java:30)
我不明白为什么我得到这个异常,当代码运行时没有
array[rows][columns] = scanner.next();
如我所料,它将遍历第 0-19 行和第 0-39 列,并且计数器将一直迭代到 900(因为文本文件是 pi 到第 900 位)。但是,当它开始将文本文件中的每个字符分配给每个元素时,当我到达第 0 行第 2 列时会抛出错误,我不知道为什么。我的 arrayinput.txt 文件的内容:
3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473
解决方案
始终检查您的扫描仪hasNext()
令牌,然后考虑调用next()
. 试试这个:
我修复了一些错误,我的编译器抱怨您没有被捕获的异常。最后在 finally 块(或您的 try-with-resources)中关闭扫描仪。
public static void main(String[] args) {
// instantiate input file
File file = new java.io.File("file.txt");
Scanner scanner = null;
// instantiate scanner to read file
try {
scanner = new Scanner(file);
// instantiate array
String[][] array = new String[20][45];
// instantiate counter
int counter = 1;
// loop to read file and assign a character to each array element
for (int i = 0; i < array.length; i++) {
for (int j = 0; j < array[i].length; j++) {
System.out.println("Row: " + i + ", column: " + j + ", counter = " + counter++);
if (scanner.hasNext()) {
array[i][j] = scanner.next();
}
} // end inner for loop
} // end outer for loop
} catch(FileNotFoundException e) {
System.err.println("There is no such file");
}finally{
scanner.close();
}
}
编辑
输出:
Row: 0, column: 0, counter = 1
Row: 0, column: 1, counter = 2
Row: 0, column: 2, counter = 3
Row: 0, column: 3, counter = 4
Row: 0, column: 4, counter = 5
Row: 0, column: 5, counter = 6
Row: 0, column: 6, counter = 7
Row: 0, column: 7, counter = 8
Row: 0, column: 8, counter = 9
Row: 0, column: 9, counter = 10
Row: 0, column: 10, counter = 11
Row: 0, column: 11, counter = 12
...