基本上,我正在尝试从如下所示的文本文件创建两个不同大小的二维数组:
2
add
3 4
2 1 7 -10
0 5 -3 12
1 7 -2 -5
0 1 2 3
4 5 6 7
8 9 0 1
subtract
2 2
2 12
10 0
4 6
9 1
2
是问题数量(加法和减法),3
和 4
是行数和列数,以及下面的数字是填充到二维数组中的两个单独的矩阵。如果我就停在那里,这个程序就可以正常工作:
class Matrices {
private Scanner fileReader;
private int rows;
private int columns;
int problems;
String method;
public Matrices(String file) throws FileNotFoundException {
this.fileReader = new Scanner(new FileInputStream(file));
problems = fileReader.nextInt();
method = fileReader.next();
if(method.equals("add")) {
rows = fileReader.nextInt();
columns = fileReader.nextInt();
}
}
public int[][] readMatrix() throws FileNotFoundException {
int[][] result = new int[rows][columns];
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
result[i][j] = fileReader.nextInt();
}
}
return result;
}
public int[][] add(int[][] a, int[][] b) {
int[][] result = new int[rows][columns];
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
result[i][j] = a[i][j] + b[i][j];
}
}
return result;
}
public void printMatrix(int[][] matrix) {
for ( int[] anArray : matrix ) {
for ( int anInt : anArray ) {
System.out.print(anInt+ " ");
}
System.out.println();
}
}
}
使用此驱动程序:
public class MatricesDriver {
public static void main(String[] args) throws FileNotFoundException {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter name of file: ");
String filename = keyboard.next();
Matrices matrixReader = new Matrices(filename);
int[][] a = matrixReader.readMatrix();
int[][] b = matrixReader.readMatrix();
System.out.println("Matrix 1: ");
matrixReader.printMatrix(a);
System.out.println();
System.out.println("Matrix 2: ");
matrixReader.printMatrix(b);
System.out.println();
System.out.println("Addition: ");
int[][] addition = matrixReader.add(a,b);
matrixReader.printMatrix(addition);
}
}
它可以很好地创建和打印矩阵,没有任何问题。但是,每当我尝试创建并打印接下来的两个矩阵(下面的 2x2 数组在文本文件中相减)时,它都会返回以下错误:
Enter name of file:
data/Matrices.txt
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.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at baker.Matrices.readMatrix(Matrices.java:27)
at baker.MatricesDriver.main(MatricesDriver.java:15
我的问题是,我应该进行哪些调整,以便程序识别出其中两个 2D 数组为 3x4,而接下来的两个数组为 2x2?
最佳答案
我建议将您的实现分解为以下部分:
- class
Matrix
- 保存问题定义中的一个矩阵的值 - class
Problem
- 保存问题定义中的运算和两个矩阵
Matrix
类可能如下所示:
class Matrix {
private int[][] values;
public Matrix(int[][] values) {
this.values = values;
}
public int[][] getValues() {
return values;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Matrix [values=\n");
for (int i = 0; i < values.length; i++) {
sb.append("\t" + Arrays.toString(values[i]) + "\n");
}
sb.append("]");
return sb.toString();
}
}
问题
类可能是:
class Problem {
private String operation;
private Matrix first;
private Matrix second;
public Problem(String operation, Matrix firstMatrix, Matrix secondMatrix) {
this.operation = operation;
first = firstMatrix;
second = secondMatrix;
}
public String getOperation() {
return operation;
}
public Matrix getFirst() {
return first;
}
public Matrix getSecond() {
return second;
}
@Override
public String toString() {
return "Problem [\noperation=" + operation + ", \nfirst=" + first + ", \nsecond=" + second + "\n]";
}
}
基于此,您的“驱动程序”类执行以下操作:
- 从用户输入中获取文件名
- 从文件中读取问题数量并以此初始大小构建一个列表
- 对于问题的数量(即 2),获取操作、行和列,并构造一个包含这些信息的新 Problem 对象,并将 Problem 放入列表中...
这是一个简单的解决方案 - 这里仍有改进的空间:-)
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
public class MatricesDriver {
public static void main(String[] args) throws FileNotFoundException {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter name of file: ");
String filename = keyboard.next();
List<Problem> problems = readProblems(filename);
System.out.println(problems);
keyboard.close();
}
private static List<Problem> readProblems(final String filename) throws FileNotFoundException {
Scanner fileReader = new Scanner(new FileInputStream(filename));
int numberOfProblems = fileReader.nextInt();
List<Problem> problems = new ArrayList<>(numberOfProblems);
for (int i = 1; i <= numberOfProblems; i++) {
problems.add(readProblem(fileReader));
}
fileReader.close();
return problems;
}
private static Problem readProblem(Scanner fileReader) throws FileNotFoundException {
fileReader.nextLine(); // go to next line
String operation = fileReader.nextLine(); // read problem operation
int rows = fileReader.nextInt(); // read number of rows
int columns = fileReader.nextInt(); // read number of columns
Matrix firstMatrix = readMatrix(rows, columns, fileReader);
Matrix secondMatrix = readMatrix(rows, columns, fileReader);
return new Problem(operation, firstMatrix, secondMatrix);
}
private static Matrix readMatrix(final int rows, final int columns, final Scanner fileReader) throws FileNotFoundException {
int[][] result = new int[rows][columns];
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
result[i][j] = fileReader.nextInt();
}
}
return new Matrix(result);
}
}
使用您的输入文件进行测试。
HTH
关于java - 可以从一个文件创建两个不同大小的数组/矩阵吗?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41812145/