My question relates to how readLine() affects the current position within a file.
Let's say I have a file which has the following in it:
1
if I say
r.readLine()
then it will return "1"
If I do another
r.readLine()
It will return 'null' as there is only one line.
So - if I check the line in an while statement like so:
while (r.readLine!=null){
//Do something here
}
So this should run until it hits a null line then exit.
However, if I want to do something like:
String line;
if ((line = r.readLine()).equals("1"))
//Then do something....
else if ((line = r.readLine()).equals("2"))
//Then do something else
What happens is that obviously,by the time I get to the 2nd check, the read position has moved to the next line.
I tried doing something like this:
String line = r.readLine();
if (line=='1')
//do Something
else if (line=="2")
//do something else.
...However, with this I get some very bizarre results. If can confirm with a System.out.println command that the string 'line' is equal to say, 1 (or whatever value). but when I try to use it in an if statement, the condition never seems to trigger....
Any help here would be appreciated.
if (line=='1')
//do Something
else if (line=="2")
//do something else.
== is used for comparing references or primitive types, you can test for String equality by using equals():
String x = "hello";
String y = "hello";
Now x == y will be true, becuase they refer to the same object in the string pool
String x = "hello";
String y = new String("hello");
Now x == y will be false, because they are not pointing to the same object anymore, one is in the string pool, while the other is not.
To test properly use equals(String):
String x = "hello";
String y = new String("hello");
x.equals(y);
will evaluate to true