<div>
Your code have several problems:<br />
<br />
1. <br />
&nbsp; while(counter&lt;newStr.lengt<wbr />h()) &nbsp;// This loop will be skipped since newStr.length() is 0 at the beginning<br />
<br />
should be <br />
<br />
&nbsp; while(counter&lt;str.length()<wbr />)<br />
<br />
2. The logic in the loop could be as follows:<br />
<br />
&nbsp; &nbsp;newStr += str.charAt(counter);<br />
&nbsp; &nbsp;if (counter+1 &lt;&nbsp;str.length()) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // check if the input string has only 1, 5, 9, ... etc &nbsp;characters<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; newStr += str.charAt(counter);<br />
&nbsp; &nbsp;counter = counter + 4;<br />

</div>


<div>
<br />
The logic has failed in the test.
</div>


<div>
public String altPairs(String str) {<br />
<br />
&nbsp; String s0=&quot;&quot;;<br />
int count = 0;<br />
<br />
While(true){<br />
if(count == str.length())return s0;<br />
if(count%4 == 0 || count %4 == 1) s0 += str.charAt(count);<br />
count++;<br />
<br />
}<br />
<br />
return s0;<br />
}
</div>


<div>
while should be of course lower case<br />
<br />
public String altPairs(String str) {<br />
<br />
&nbsp; String s0=&quot;&quot;;<br />
int count = 0;<br />
<br />
While(true){<br />
if(count == str.length())return s0;<br />
if(count%4 == 0 || count %4 == 1) s0 += str.charAt(count);<br />
<br />
<br />
}<br />
<br />
return s0;<br />
}
</div>


<div>
Could not test from my mobile device and could not make while lowere case - it for some reason makes it upper case when I click &nbsp;post
</div>


<div>
Dear for_yan: The second return stmt is unreachable. Perhaps, the code all stuck in infinite loop.<br />
Take your time. :-)<br />
<br />
public String altPairs(String str) {<br />
String s0=&quot;&quot;;<br />
int count = 0;<br />
<br />
While(true){<br />
if(count == str.length())return s0;<br />
if(count%4 == 0 || count %4 == 1) s0 += str.charAt(count);<br />
<br />
<br />
}<br />
<br />
return s0;<br />
} <br />
<br />
Dear CEHJ:<br />
Yes, the code is working.Thanks !<br />
<br />
Regards,<br />
<br />
yjchong514
</div>


<div>
When pasting it lost count++; line as the last line in the loop
</div>


<div>
public String altPairs(String str) {<br />
<br />
  String s0=&quot;&quot;;<br />
int count = 0;<br />
<br />
While(true){<br />
if(count == str.length())return s0;<br />
if(count%4 == 0 || count %4 == 1) s0 += str.charAt(count);<br />
<br />
count++;<br />
}<br />
<br />
return s0;<br />
} 
</div>


<div>
for_yan:<br />
can you explain the purpose of<br />
if(count == str.length())return s0;<br />
<br />
thank you.
</div>


<div>
Wish everyone have a nice working days. :-)
</div>


<div>
Also avoid uncounted loops of the for(;;) or while(true) sort - they make your code less readable and can lead to nasty errors
</div>


<div>
:) There is however, a part of for_yan's code that's superior to mine, and you should adopt it. e.g.<br />

<pre><code class="code-1 nolinks" id="code-8191036"><span>public String altPairs(String str) {</span>
<span>  StringBuilder result = new StringBuilder();</span>
<span>  for(int i = 0;i &lt; str.length();i++) {</span>
<span>      if((i % 4 == 0) || (i % 4 == 1)) {</span>
<span>        result.append(str.charAt(i));</span>
<span>      }</span>
<span>  }</span>
<span>  return result.toString();        </span>
<span>}</span>
</code></pre>
</div>


<div>
<div class="content wysiwyg-content">
Dear EE members,<br />
<br />
I would like to establish: <a href="http://codingbat.com/prob/p121596" rel="ugc">http://codingbat.com/prob/p121596</a><br />
<br />
Here is my code:<br />
public String altPairs(String str) { //01 23 45 67 89 i=0,1 i=i+4,i+5<br />
&nbsp; String newStr = &quot;&quot;;<br />
&nbsp; int counter = 0;<br />
&nbsp; <br />
&nbsp; while(counter&lt;newStr.lengt<wbr />h()){<br />
&nbsp; &nbsp; if(counter==0||counter==1)<wbr /> newStr += str.charAt(0); &nbsp; <br />
&nbsp; &nbsp; <br />
&nbsp; &nbsp; counter=counter+4;<br />
&nbsp; &nbsp; newStr += str.charAt(counter);<br />
&nbsp; } &nbsp;<br />
&nbsp; <br />
&nbsp; return newStr;<br />
}<br />
<br />
Regards,<br />
<br />
yjchong514
</div>
</div>


Dear EE members,

I would like to establish: http://codingbat.com/prob/p121596

Here is my code:
public String altPairs(String str) { //01 23 45 67 89 i=0,1 i=i+4,i+5
  String newStr = "";
  int counter = 0;
  
  while(counter<newStr.length()){
    if(counter==0||counter==1) newStr += str.charAt(0);   
    
    counter=counter+4;
    newStr += str.charAt(counter);
  }  
  
  return newStr;
}

Regards,

yjchong514

String Processing

Java is a platform-independent, object-oriented programming language and run-time environment, designed to have as few implementation dependencies as possible such that developers can write one set of code across all platforms using libraries. Most devices will not run Java natively, and require a run-time component to be installed in order to execute a Java program.