Index out of bound exception in java

Question

pred[] is a char array taken as input from the user. the expected input is in form predicate(param1,param2). this while loop is to detect the start and end indices of predicate, param1, and param2 but for some reason it is giving an exception.

    int k =0;
    while(pred[k]!="\0"){
            System.out.println("k="+k);
            if ("(".equals(pred[k])) {
                param1_st = k + 1;
                pred1_end = k - 1;
            }
            if (",".equals(pred[k])) {
                param1_end = k - 1;
                param2_st = k + 1;
            }
            if (")".equals(pred[k])) {
                param2_end = k - 1;

            }
            k++;

        }

output:

Enter a predicate 1
abd(sd,sdf)
Entered predicate is: abd(sd,sdf)
Enter a predicate 2
abd(x,db)
Entered predicate is: 
abd(x,db)k=0
k=1
k=2
k=3
k=4
k=5
k=6
k=7
k=8
k=9
k=10
Exception in thread "main" 
java.lang.ArrayIndexOutOfBoundsException:11
at unification.Unif.main(Unif.java:41)

what's \0 supposed to mean? are you checking for the end of the line? — Aequitas, Aug 19 '15 at 23:13
`while(pred[k]!="\0"){` -> [How do I compare strings in Java?](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java). Based on `if ("(".equals(pred[k]))` you seem to know how. — Pshemo, Aug 19 '15 at 23:14
shouldn't it be n then? also can you not use the length of the array? like -> `while(k < pred.length - 1)`? — Aequitas, Aug 19 '15 at 23:16
what i don't understand is that why is it giving an index out of bound exception — Rohitashwa Pandey, Aug 19 '15 at 23:16
Because you have 10 elements in the array pred but you are doing pred[11] which doesn't exist — Aequitas, Aug 19 '15 at 23:17
Also based on that very link you referenced it says not to use `==` to compare strings so why are you doing just that? use `!("\0".equals(pred[k])` — Aequitas, Aug 19 '15 at 23:22
your while loop will go forever because your condition will never be `!(false)` — Aequitas, Aug 19 '15 at 23:23
Is `pred` a char array, or a String array? If it is actually a char array, then comparing `"\0"` is completely nonsensical -- and Java doesn't use null-terminated strings anyway. — Louis Wasserman, Aug 19 '15 at 23:25
@LouisWasserman it must be a string array but it's still nonsensical because unless `pred[x] = "\0";` was done somewhere it will not be the same object as "\0". and since it's being read in from the console it won't equal. — Aequitas, Aug 19 '15 at 23:32

owenrb · Answer 1 · 2015-08-20T00:41:45.607

0

The condition in the while loop evaluates to a string comparison and in this case it will always return true value. A result is an infinite loop, since the k variable keeps incrementing, the index pointer will cause out-bound-exception when it goes beyond the array size limit.

while(pred[k]!="\0")

try to evaluate using length property instead.

while(k < pred.length )

edited Aug 20 '15 at 00:41

answered Aug 20 '15 at 00:32

owenrb

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Index out of bound exception in java

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