递归方法的返回值

Question

我有一个递归方法，我想在特定的 if 语句返回 true 时返回一个值（它总是这样做）

    if (compactArray != null) {
            if (arrayCount == (compactArray[0].length - 1)) {
                return compactArray;//i want to return here
            }
        }

但 Java 不会让我从 if 返回，并抛出警告，提示我需要添加返回值。

一个人做什么？完整方法如下

public String[][] diXmlRecursiveRead(Iterator<Element> list, String[] columnNames, String[][] compactArray,
        Integer arrayCount) {
    Element element = null;
    String[] columns = null;

    while (list.hasNext()) {
        element = list.next();

        // Assign data to the two dimensional array, starting from position
        // 1 in the length to not overwrite the column names.
        // This is also where i would print the column name plus its
        // attribute value if i was printing to console.
        if (columnNames != null) {
            for (int a = 0; a < columnNames.length; a++) {
                compactArray[a][arrayCount] = element.getAttributeValue(columnNames[a]);
            }
        }

        // Find the element that contains the columns="" information
        if (element.getAttributeValue("columns") != null) {
            // reset the array count, since we are processing a new
            // columns="" section
            arrayCount = 1;

            columns = element.getAttributeValue("columns").toString().split(",");

            // set width size +1 to make room for the column names
            // (columnNames + data +1)
            compactArray = new String[columns.length][element.getChildren().size() + 1];

            // Set the EVE column names in the first column of the two
            // dimensional array
            for (int a = 0; a < columns.length; a++) {
                compactArray[a][0] = columns[a];
            }
        }

        // After added the last value to the two dimensional array return the
        // array[][]
        if (compactArray != null) {
            if (arrayCount == (compactArray[0].length - 1)) {
                return compactArray;//i want to return here and not at the end!
            }
        }

        // Method calls itself with a new level of the child
        diXmlRecursiveRead(element.getChildren().iterator(), columns, compactArray, arrayCount++);
    }
    //Java want me to return here!!
}

Answer 1

看那个例子：

static int count = 0;
private static boolean foo() {
    if (count == 5) {
        return true;
    }
    count ++;
    return foo();
}

请注意，递归调用是使用“return”语句调用的。
考虑一下执行递归方法时正在构建的堆栈。在某些时候，所有方法都需要开始在堆栈上返回一个值。