Question

我在netbeans中编写程序，但我无法在.txt文件中打印它。 indead，我的编程代码确实正常工作。我认为问题出在最后一行代码中。这是我的代码：

import java.io.*;
import java.util.*;

public class converttopathbased_bfs 
{

    static String START;
    static String END;
    static int numberOfNodes;
    static int numberOfArcs;
    static int numberOfCommodities;
    static int OriginDestinationOfCommodities[][] = new int[numberOfCommodities][2];
    static int neighborhoods[][] = new int[numberOfNodes][numberOfNodes];
    static int variableCosts[][] = new int[numberOfNodes][numberOfNodes];
    static int capacities[][] = new int[numberOfNodes][numberOfNodes];
    static int fixedCosts[][] = new int[numberOfNodes][numberOfNodes];
    static int demandOfCommodities[] = new int[numberOfCommodities];
    java.io.File file = new java.io.File("pathBasedTest.txt");
     java.io.PrintWriter output;


    public static void main(String[] args) throws Exception
    {
        java.io.File data = new java.io.File("samples//test.txt");
        Scanner scanner = new Scanner(data);

        numberOfNodes = scanner.nextInt();

        numberOfArcs = scanner.nextInt();

        numberOfCommodities = scanner.nextInt();

        Graph graph = new Graph();

        for (int i = 0; i < numberOfArcs; i++)
        {
            int m = scanner.nextInt() - 1;
            int n = scanner.nextInt() - 1;

            String S = "";
            String E = "";

            S = Integer.toString(m + 1);
            E = Integer.toString(n + 1);

            scanner.nextInt();

            scanner.nextInt();
            scanner.nextInt();

            graph.addEdge(S, E);

                scanner.nextInt();
            scanner.nextInt();
        }


        for (int i = 0; i < numberOfCommodities; i++)
        {            
            converttopathbased_bfs.START = scanner.next();
            converttopathbased_bfs.END = scanner.next();
            scanner.nextInt();

        LinkedList<String> visited = new LinkedList();
        visited.add(START);
        new converttopathbased_bfs().breadthFirst(graph, visited);
        }
    }

    private void breadthFirst(Graph graph, LinkedList<String> visited)  throws Exception
    {
        output = new java.io.PrintWriter (file) ;
        LinkedList<String> nodes = graph.adjacentNodes(visited.getLast());
        // examine adjacent nodes 
        for (String node : nodes)
        {
            if (visited.contains(node))
            {
                continue;
            }
            if (node.equals(END))
            {
                visited.add(node);
                printPath(visited);
                visited.removeLast();
                break;
            }
        }
        // in breadth-first, recursion needs to come after visiting adjacent nodes 
        for (String node : nodes)
        {
            if (visited.contains(node) || node.equals(END))
            {
                continue;
            }
            visited.addLast(node);
            breadthFirst(graph, visited);
            visited.removeLast();
        }
    }

    private void printPath(LinkedList<String> visited) 
    {       
        for (String node : visited)
        {
            output.printf("s", node);
            output.printf(" ");
        }
        output.printf("\n");
    }
}

Answer 1

主要问题是，每次调用output时都会创建breadhtfirst。您应该只在代码的开头创建一次，然后在代码的末尾关闭它。

你可能想要最后几行：

for (String node : visited)
{
    output.printf("%s ", node);
}
output.println();

但我们需要更多信息才能确定。

您还需要在代码末尾关闭该文件。

output.close();

Answer 2

尝试关闭文件流：

output.close()

Answer 3

您需要添加以下两行：

output.flush();


output.close();

将其转换为BufferedWriter并使用append方法。

打印输出到java中的.txt文件的问题

3 个答案: