如何使用printwriter将数据写入输出文件[保留]

Question

        PrintWriter out = new PrintWriter(outputFile);

        String result = "";

        for (Orders o : allOrders) {
            result += o + "\n";
            out.print(result);
        }

this is what i have so far and the result to the file should look like:

pizza

hamburger

sandwich

quesadilla

but when i ran my test cases it said that line 2 was actually "pizza", so basically I'm wondering if my code is somehow incorrect?

UPDATE: so it passed now i was forgetting out.close() lol

Answer 1

Here is your code:

  String result = "";

    for (Orders o : allOrders) {
        result += o + "\n";
        out.print(result);
    }

At the end of the first loop, Result is pizza\\n. After the second time, it's pizza\\nhamburger\\n.

So you'll print:

pizza <-- from the first print
pizza <-- start of second print
hamburger
pizza <-- start of third print
hamburger
sandwich
pizza <-- start of fourth print
hamburger
sandwich
quesadilla

The problem is the +=. Change it to a simple = and see how that works.

Answer 2

You could simply do this:

PrintWriter out = new PrintWriter(outputFile);

for (Orders o : allOrders) {
    out.print(o + "\n");
}

If you want two returns like your output that you gave shows, you can simply add another "\\n".