java - 使用 Java Scanner 读取文件时，处理完最后一行后挂起

Question

我的方法能够读取文件的所有行，但随后它会卡在最后一行，并且永远不会到达 scanner.close() 及以后。我不知道为什么？我调用 scanner.nextLine() ，因此它肯定应该检测到这一点，并且当文件结束时， scanner.hasNextLine() 应该返回 false 。有没有我忽略的快速修复方法？

private int[] GetNumberOfRowsAndColumns(BufferedReader br) {
    Scanner scanner = new Scanner(br);
    String line = "";
    int column_max = 0;
    int total_rows = 0;
    int[] result = new int[1];

    try {
        while (scanner.hasNextLine()) {
            line = scanner.nextLine();
            if (line.length() > column_max) {
                column_max = line.length();
            }
            total_rows++;
        }
    } catch (Exception e) {
        System.err.println(e);
    }
    scanner.close();
    result[0] = column_max;
    result[1] = total_rows;

    return result;
}

有问题的文件:

+++++++++++++++++
+0A             +
+AA          ++++
+               +
+            ++A+
+             +a+
+++++++++++++++++

编辑:

public SearchClient(BufferedReader serverMessages) throws Exception {
    Map<Character, String> colors = new HashMap<Character, String>();
    String line, color;

    int agentCol = -1, agentRow = -1;
    int colorLines = 0, levelLines = 0;

    // Read lines specifying colors
    while ((line = serverMessages.readLine())
            .matches("^[a-z]+:\\s*[0-9A-Z](,\\s*[0-9A-Z])*\\s*$")) {
        line = line.replaceAll("\\s", "");
        String[] colonSplit = line.split(":");
        color = colonSplit[0].trim();

        for (String id : colonSplit[1].split(",")) {
            colors.put(id.trim().charAt(0), color);
        }
        colorLines++;
    }

    if (colorLines > 0) {
        error("Box colors not supported");
    }
    int[] result = getNumberOfRowsAndColumns(serverMessages);
    System.err.println("MAX COLUMNS = " + result[0]);
    System.err.println("MAX ROWS = " + result[1]);

    initialState = new Node(null);

    while (!line.equals("")) {
        for (int i = 0; i < line.length(); i++) {
            char chr = line.charAt(i);
            if ('+' == chr) { // Walls
                initialState.walls[levelLines][i] = true;
            } else if ('0' <= chr && chr <= '9') { // Agents
                if (agentCol != -1 || agentRow != -1) {
                    error("Not a single agent level");
                }
                initialState.agentRow = levelLines;
                initialState.agentCol = i;
            } else if ('A' <= chr && chr <= 'Z') { // Boxes
                initialState.boxes[levelLines][i] = chr;
            } else if ('a' <= chr && chr <= 'z') { // Goal cells
                initialState.goals[levelLines][i] = chr;
            }
        }
        line = serverMessages.readLine();
        levelLines++;
    }
}

Answer 1

按照惯例，Java 方法以小写字母开头。接下来，您的数组只能保存一个值(长度为 1)，并且您不需要 Scanner(使用您的 BufferedReader)。最后，您可以创建一个匿名数组。比如，

private int[] getNumberOfRowsAndColumns(BufferedReader br) {
    int column_max = 0;
    int total_rows = 0;

    try {
        String line;
        while ((line = br.readLine()) != null) {
            // if (line.length() > column_max) {
            //  column_max = line.length();
            // }
            column_max = Math.max(column_max, line.length());
            total_rows++;
        }
    } catch (Exception e) {
        System.err.println(e);
    } finally {
        try {
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return new int[] { column_max, total_rows };
}