CODEWITHSUNDEEP
javastringmethods
user4147933
user4147933

Reputation: 15

Write a method that returns the even indexes of a string

So I'm supposed to write a method that only prints out the even indexes of a string. So for instance if I input “Hiejlzl3ow” into the console/scanner I would want to return "Hello". I got the solution by using a for loop and charAt(i), however I am having trouble returning the result as a String (as it is a char). I tried converting the charAt(i) using String.valueOf but it only prints out the first (or rather the 0) index value (in this case H). Does anyone have a quick fix for this? And is there a simpler solution? (Note: This is beginning java so only methods, for loops, string methods, and scanners are allowed.)

//This method prints out the even indexes of a string
public static String decrypt(String question, Scanner console)
{
  System.out.print(question + " ");
  String s = console.nextLine();
  for (int i = 1; i < s.length()-1; i=i+2)
  {
     char x = (s.charAt(i));
     s = String.valueOf(x);

  }
return s;
}

Upvotes: 1

Views: 4937

Answers (8)

Scott Woolsey
Scott Woolsey

Reputation: 1

Since this is beginning Java, you might try this:

//This method prints out the even indexes of a string
public static String decrypt(String question, Scanner console)
{
  System.out.print(question + " ");
  String s = console.nextLine();
  for (int i = 0; i < s.length(); i+=2)
    {
         System.out.print(s.charAt(i));
    }
}

Upvotes: 0

Hitesh Garg
Hitesh Garg

Reputation: 1211

Your problem is obvious as you are a beginner. Let me explain you a bit

  • In java String starting index starts from ZERO(0) but you are using int i=1 in your for loop.
  • Either use i < s.length() or i <= s.length()
  • Thirdly when you take out a character from the input string you convert it into a String and assign it to its variable due to which only last character processed remains in the String since the Strings are immutable in Java. So you have to concatenate every new character in the String processed so far.
  • This one is just for optimisation(you can skip it as a beginner) that you can use StringBUffer or StringBuilder classes so that no new object is created every time you concatenate a character into the String.

You can read more about StringBuffer and StringBuilder and how to use them in Java

Try out this code -

public static String decrypt(String question, Scanner console)
{
  System.out.print(question + " ");
  String s = console.nextLine();
  String result ="":
 for (int i = 0; i < s.length(); i=i+2)
  {
     result  += s.charAt(i);
  }
return result;
}

Follow this link to read other interesting Java String stuff

Upvotes: 0

ataulm
ataulm

Reputation: 15334

String blah = "hbellalho";
String evenIndices;
for (int i = 0; i < blah.length; i++) {
    if (i % 2 != 0) {
        evenIndices += blah.getCharAt(i);
    }
}
return evenIndices;

Your main issue is that you were modifying the original string. You need another (or even better, a StringBuilder, though I didn't include this for simplicity) to hold only even values.

When you do += with a String in Java, remember that it will create a new String object each time, so this is not great to have in loops with large iterations.

Upvotes: 0

Karthik
Karthik

Reputation: 76

First of All, String index is start from 0. So in for loop you need to set i value to 0. Second mistake in your code is your modifying the string 's' value in for loop. that's why your getting 'i' as output.

Try following code, you will get expected output

   //This method prints out the even indexes of a string
public static String decrypt(String question, Scanner console)
{
  String str = "";
  System.out.print(question + " ");
  String s = console.nextLine();
  for (int i = 0; i < s.length(); i=i+2)
  {
     char x = (s.charAt(i));
     str  = str + String.valueOf(x);

  }
return str;
}

Upvotes: 1

DeepInJava
DeepInJava

Reputation: 1961

You should use i=o to initialize array and i < s.lenght() as condition to iterate through complete string.

Upvotes: 0

Jens
Jens

Reputation: 69460

Array's in java are zero based. So you should start the index with 0:

for (int i = 0; i < s.length()-1; i=i+2)
             ^^

Upvotes: 0

Darshan Lila
Darshan Lila

Reputation: 5868

Try following code:

public static String decrypt(String question, Scanner console)
    {
      System.out.print(question + " ");
      String s = console.nextLine();
      StringBuilder builder=new StringBuilder("");
      for (int i = 0; i < s.length(); i++)
      {
          if(i%2==0){
              builder.append(s.charAt(i));
          }
      }
    return builder.toString();
    }

Input :

Hello World

Output :

HloWrd

For more on StringBuilder visit this link.

Upvotes: 0

Eng.Fouad
Eng.Fouad

Reputation: 117597

You can use a StringBuilder:

StringBuilder sb = new StringBuilder();

// ...

sb.append(x);

// ...

String result = sb.toString();

Upvotes: 0

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