End while loop at end of string

Question

I want to end whileloop, regardless of the length. For python a (-1) is returned when the index exceeds the length of the string. But I can't find to work out how to do the same in java.

 while(true) {
        System.out.println("Letter nur " + (i+1) + " is " + name.charAt(i));
        if(name.charAt(i)==-1){
            break
        }
        i = i + 1;

Can I and if yes, how?

When iterating over a sequence of fixed length, use a `for` loop instead of a `while` loop. This is true for both Python and Java. — Code-Apprentice, Jan 16 '18 at 20:52
I don't see how you could get a -1 in Python. There is no `charAt` method on string, and indexing past the end would raise an exception. — Fred Larson, Jan 16 '18 at 20:55
@FredLarson Perhaps the OP is confused with slicing syntax where you can use `-1` as an index? — Code-Apprentice, Jan 16 '18 at 20:57
@Code-Apprentice: Maybe, but that doesn't seem to relate well to this question. — Fred Larson, Jan 16 '18 at 20:58

score 2 · Answer 1 · answered Jan 16 '18 at 20:53

2

Use a for loop:

for (int i = 0; i < name.length(); i++) {
    System.out.println("Letter nur " + (i+1) + " is " + name.charAt(i));
}

answered Jan 16 '18 at 20:53

shmosel

49,289
6
73
138

Can you do `for (char c : s)` in Java? It has been too long since I wrote any Java code. – Code-Apprentice Jan 16 '18 at 20:55
@Code-Apprentice You can do `for (char c : s.toCharArray())`. But then you can't print `i+1`. – shmosel Jan 16 '18 at 20:57
You could also just put the test part of this `if` in the `while`. But I think range-for is the best idea. – Fred Larson Jan 16 '18 at 21:00
Thanks! I'm doing an exercise where I'm suppose to compare the time for while and for loops. But if i were to compare while(i < name.length() and for(int i = 0; i < name.length(); i++) wouldnt that be almost the same thing? – parvelmarv Jan 16 '18 at 21:02
@parvelmarv Yes. The `for` loop is just more conventional. – shmosel Jan 16 '18 at 21:05
@parvelmarv: Perhaps that's one point of the exercise -- to see the relationship between `while` and `for`. Also, see https://stackoverflow.com/q/1165457/10077 – Fred Larson Jan 16 '18 at 21:06
Since you are comparing the timing of for vs while, you should still keep the logic as close as possible. This means using `while(i < name.length())` rather than an `if` statement with a break. Of course, you could compare all three of these options to see if there is any difference in the timing. – Code-Apprentice Jan 16 '18 at 22:33

score 0 · Answer 2 · answered Jan 16 '18 at 21:21

You can easily use length() function for this purpose. But according to question, you want to end while loop at the end of string. This can be done as follows:

    int i=0;
    while(true){
        try{
            System.out.print(""+as.charAt(i));
            i++;
        }
        catch(java.lang.StringIndexOutOfBoundsException e){
            break;
        }
    }

End while loop at end of string

2 Answers2