BufferedReader readLine() - Exit when a specific string is entered

Question

As title, I want it to exit the loop when I entered a specific keyword.

try {
    buf = br.readLine();
    while (buf != "doh") {
        buf = br.readLine();
    }
}

Two questions:

When I enter doh from my command prompt, it doesn't exit the loop.
If I put "buf != null" it works only if I press Ctrl+Z. If I enter nothing (just press enter key) it doesn't exit the loop.

The second point is because pressing just enter gives you "\n", but since readLine method deletes the "\n" at the end you just get "" (an empty string), which is different form null. For the first one, just check the answers. — raven1981, Sep 22 '12 at 22:42

score 3 · Accepted Answer · edited May 23 '17 at 11:59

3

Change:

buf != "doh"

to:

!buf.equals("doh")

And read: Java String.equals versus ==.

edited May 23 '17 at 11:59

Community

1
1

answered Sep 22 '12 at 22:32

Tomasz Nurkiewicz

334,321
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gkuzmin · Answer 2 · 2012-09-22T22:47:32.330

2

Use equals method instead of !=. Operator != will return true only if references to object will not be identical. Method equal wil compare strings char by char.

edited Sep 22 '12 at 22:47

answered Sep 22 '12 at 22:33

gkuzmin

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score 2 · Answer 3 · answered Sep 22 '12 at 22:34

You shouldn't compare strings (and objects in general) with ==, that is utilized only for primitives (int, char, boolean etc.). For objects, you use the equals method.

try {
    buf = br.readLine();
    while (! buf.equals("doh")) {
        buf = br.readLine();
    }
}

BufferedReader readLine() - Exit when a specific string is entered

3 Answers3