Site Map
Useful Tools
Graphing Calc
Scientific Calculator
What would be the following method calls
Will the code below cause any run time errors? If so, explain.
Yes, this will cause a StringIndexOutOfBounds error for any string with a length greater than 0.
str.substring( i , i+ 3 ) requires that the loop end at .length() -2
public String foo(String str){
String r="";
for( int i = 0 ;i < str.length() ;i ++ )
{
r += str.substring( i , i+ 3 ) ;
}
return r;
}
| Answer |
str.substring( i , i+ 3 ) requires that the loop end at .length() -2
public String foo(String str){
String r="";
for( int i = 0 ;i < str.length()-2 ;i ++ )
{
r += str.substring( i , i + 3 ) ;
}
return r;
}
Look at both of the methods below. Which of them correctly returns a String in reverses order. Ie "abcd" 
"dcba"
Method I
Method 2
"dcba" Method I
public String reverse(String str){
String r ="";
for( int i = str.length(); i> 0 ; i--)
{
r += str.substring(i-1,i);
}
return r;
}
Method 2
public String reverse(String str){
String r ="";
for( int i = str.length()-1; i>= 0 ; i--)
{
r += str.substring(i,i+1);
}
return r;
}
| Answer |
Method 1 works perfectly fine.
Method 2 does reverse the letters but it misses the first letter, the loop. For Method 2 towork correctly, the loop should be changed to i >= 0. .
Method 2 does reverse the letters but it misses the first letter, the loop. For Method 2 towork correctly, the loop should be changed to i >= 0. .
** Extra Credit Level
public String myString(String str)
public String myString(String str)
public String mystery(String str){
String r="";
for( int i = 0 ;i < str.length() -2 ;i += 2 )
{
r += str.substring( i , i+ 3 ) ;
}
return r;
}
| Method Call | return value/output |
| mystery("abc123xyz") | ????? |
| Answer |
abcc1223xxyz