CODEWITHSUNDEEP
java
Joe
Joe

Reputation: 109

calculate the number of characters in a string recursively

I am trying to calculate the number of characters in a string by using recursive method. here is my code in java

public class MainClass {

    public int length(String str) {
        if (str == null) {
            return 0;
        } else {   
            return length(str.substring(1))+1; // in eclipse it says : at MainClass.length(MainClass.java:12)
        }
    }

    public static void main(String args[]) {    
        MainClass m = new MainClass();
        System.out.println(m.length("ali"));    
    }
}

This line does not work : return length(str.substring(1))+1; How can I correct the code? Thanks

Upvotes: 1

Views: 107

Answers (2)

ravthiru
ravthiru

Reputation: 9633

It should be 

public int length(String str) {

if (str==null||str.isEmpty()) {
   return 0;
 }else {  
 return length(str.substring(1))+1
}

Upvotes: 1

f1sh
f1sh

Reputation: 11934

You forgot the case when your String argument is an empty string, include that in your check:

if (str == null || str.length()==0) {
  return 0;
} else {   
[...]

Please note that the Exception that you get contains valuable information about what's going wrong, in this case it's probably a StringIndexOutOfBoundsException because you call substring(1) on an empty String object.

Upvotes: 3

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