我有一个名为“multiarray”的二维数组。第一个是[7]，第二个是当前初始化为[500]。我正在从一个文本文件中读取，该文件随机数量的条目将转到第二个数组。该数组永远不会有500个条目，我需要知道有多少条目。
我在想y < multiarray[x].length会告诉我我需要知道什么，但它似乎在循环。
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Formatter;
import java.util.Scanner;
public class DOW
{
public static void main(String[] args)
{
File file = new File ("/Users/***/RandomInts.txt") ;
try
{
Scanner scanner = new Scanner(file) ;
//Formatter formatter = new Formatter (new File ("outputfile.txt")) ;
int [][] multiarray = new int [7][500];
int counter1 = 0;
int counter2 = 0;
int counter3 = 0;
int counter4 = 0;
int counter5 = 0;
int counter6 = 0;
int counter7 = 0;
while (scanner.hasNext())
{
int dow = scanner.nextInt () ;
int temp = scanner.nextInt () ;
dow = dow -1;
if(dow == 0)
{
multiarray[dow][counter1] = temp;
counter1 ++;
}
if(dow == 1)
{
multiarray[dow][counter2] = temp;
counter2 ++;
}
if(dow == 2)
{
multiarray[dow][counter3] = temp;
counter3 ++;
}
if(dow == 3)
{
multiarray[dow][counter4] = temp;
counter4 ++;
}
if(dow == 4)
{
multiarray[dow][counter5] = temp;
counter5 ++;
}
if(dow == 5)
{
multiarray[dow][counter6] = temp;
counter6 ++;
}
if(dow == 6)
{
multiarray[dow][counter7] = temp;
counter7 ++;
}
}
for (int x = 0; x < 7; x++)
{
int hightemp = 0;
int lowtemp = 0;
int avetemp = 0;
for (int y = 0; y < multiarray[x].length ; y++)
{
if (multiarray[x][y] > hightemp)
{
hightemp = multiarray[x][y];
}
if (multiarray[x][y] < lowtemp)
{
lowtemp = multiarray[x][y];
}
avetemp = avetemp + multiarray[x][y];
}
//avetemp = avetemp /
}
//formatter.format (" %d %d \n " , dow , temp ) ;
//formatter.flush () ;
//formatter.close () ;
//int[] dow;
//dow = new int [7];
//int[] temp;
//temp = new int [100];
//int x = 0;
//while ( x < temp.length)
//{
//System.out.println (temp[x]);
//++x;
//temp[x]=0;
//}
}
catch (FileNotFoundException e)
{}
}
}
我想知道数组长度的原因是因为我想在数学中调用数字。
avetemp = avetemp / multiarray[x].length
我已经为[x]提供了一个计数器，因为它正在从文件读入，但我希望不要在这里使用它，这样我就不必手动写出所有内容。
输入文本文件的示例：
5 67
2 -15
1 -40
7 32
6 -24
7 33
5 -32
3 57
3 41
6 51
基本上第一列是星期几，第二列是温度。
答案 0 :(得分：1)
现在我知道你的输入是什么样了。
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;
public class DOW {
public static void main(String[] args) {
File file = new File("/Users/***/RandomInts.txt");
try {
Scanner scanner = new Scanner(file);
ArrayList<Integer>[] multiarray = new ArrayList[7]; // This is how one would make an array of ArrayList's.
for (int i = 0; i < multiarray.length; i++)
multiarray[i] = new ArrayList<Integer>();
while (scanner.hasNextInt()) { //This is how you would save the values. You were saving temperatures incorrectly.
int dow = scanner.nextInt() - 1; //Get day of week.
int temp = scanner.nextInt(); //Get temperature. [Would throw exception here if your input was bad]
multiarray[dow].add(temp); //Store temperature in the array representing the day of week.
}
// Looks like you want to find min, max and average in each column here.
for (int x = 0; x < 7; x++) {
int hightemp = Integer.MIN_VALUE; // Set this to something really low. (You will see why in a minute)
int lowtemp = Integer.MAX_VALUE; // Set this to something really high.
double avetemp = 0; // You seem to be using ave as "sum" right now and then you plan on dividing which is fine. This should also be a double.
int size = multiarray[x].size(); // No point calling .size() [or in general any function] over and over again. Its better to just cache the answer.
for (int y = 0; y < size; y++) {
int num = multiarray[x].get(y); // Same logic as size here.
hightemp = Math.max(hightemp, num);
lowtemp = Math.min(lowtemp, num);
avetemp += num;
}
avetemp = avetemp / size;
// P.S.: Also you probably want to save the values of hightemp, lowtemp, avetemp somewhere after doing all this work!
// Removed the rest of your code as it is irrelevant for your question.
}
// Close your streams.
scanner.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (Exception e) {
// This would happen if your input file is bad.
e.printStackTrace();
}
}
}
编辑：您正在正确添加内容。我的坏。
答案 1 :(得分：0)
此代码没有太大问题，但是如果初始化长度为500的y数组，则无论实际填充了多少元素，都将返回长度。如果需要，请在读取文件后初始化数组，或使用java.util.List。如果值不可能为0，那么您也可以迭代所有非0值，并在第0位停止。
答案 2 :(得分：0)
java中的数组是静态的，这意味着已预先分配了您声明的空间，因此，无论您实际插入多少条目，多数组[y] .length将始终为500.您可以使用ArrayList或者是LinkedList而已.Their空间全部动态分配，因此它们的长度将告诉你它们实际包含的条目数。
答案 3 :(得分：0)
数组具有固定大小 - 您将第二个维度的数组初始化为500.在该数组上调用长度将始终返回500.如果您需要更动态的数据结构，请考虑使用ArrayList。当你添加它时，size（）返回的值将递增。
如果您不想切换到ArrayList，则可以将数组更改为三维数组，第三个维度的长度为1.这可能是您维护第二维的大小的位置。
-
我不知道这是否会导致您的错误，但您的代码中确实存在错误。最后的while循环尝试访问临时数组外部：
int x = 0;
while (x < temp.length) {
System.out.println(temp[x]);
++x;
temp[x] = 0;
}
由于你的++ x，它从1循环到（temp.length + 1）。
改为使用for循环：
for(x=0; x<temp.length; x++)
{
System.out.println(temp[x]);
temp[x] = 0;
}