从文件Java中检测特定的字符串值

Question

I'm trying to detect a particular string value in an external txt file. In this case, I am trying to detect %%.

public void read(){
    while(x.hasNext()){
        String a = x.next();
        System.out.println(a);
        if(a == "%%"){
            System.out.println("Found the end");
        }
        else{
            System.out.println("No end");
        }

    }
}

It is reading x correctly because it prints out the words from the file, but it says "No end" after every word, even the "%%". I'm sure I am making some dumb mistake somewhere, I just can't find it. x looks like this: apple orange %% grapes. Any help with this would be appreciated.

Answer 1

You have to use String::equals() for comparison but not the operator == . The == operator compares the address location of String and the string literal %% in your case.

Answer 2

Try

    if(a.trim().equals("%%"))
    {
        System.out.println("Found the end");
    }

That should get rid of any excess whitespace at the end of the string as well as ensure a good comparison!

Answer 3

You should use logical eqality using equals method rather than == which check for reference .

if(a.equals("%%")){
        System.out.println("Found the end");
    }
    else{
        System.out.println("No end");
    }