What is the best way to check if a string index is in bounds? Let's say we are checking a String for index i-1
or i+1
because you cannot say != null.
Example:
for (int i = 0; i < string.length(); i++)
{
if (string.charAt(i+1) == '#' && string.charAt(i - 1) != '1')
{
}
}
Should you just check the length of the string and see if it is within it?
string.charAt(i+1) == '#'
Yes, I think you need to make sure i+1
is not greater than String length.
Example:
if( (i+1) < string.length() && (i-1) >= 0 && (yourcode))
{
}
为什么不只检查字符串的长度?
if(myString.length() - 1 > i)
I've always modified the length (and/or start) of the loop in these cases... these are all good answers - there's no one way to do it, but this is how I would do it:
for (int i = 1; i < string.length() - 1; i++)
{
if (string.charAt(i+1) == '#' && (i != 1 || string.charAt(i - 1) != '1'))
{
}
}
EDIT: After considering all of the situations that this code entails, I wouldn't necessarily do this in this manner, but find a cleaner way to express exactly what I'm trying to accomplish
The simplest way is to change your for
loop like this:
for (int i = 1; i < string.length() - 1; i++)
{
if (string.charAt(i+1) == '#' && string.charAt(i - 1) != '1')
{
}
}
Explanation:
string.charAt(i - 1)
implies that you might read position i-1
of the string. Since 0 is the lowest valid value you can start the iteration with i = 1
string.charAt(i + 1)
implies that you might read position i+1
of the string. Since string.length() - 1
is the highest valid value you need to end your iteration at i == string.length() - 2
. Since the for-loop checks the condition before entering the loop using i < string.length() - 1
will be just right.
I would try with this code.
for (int i = 1; string!= null && string.length() >= 3 && i < string.length() - 1; i++)
//it solve the case of String == null and string too short
//it optimize the max number of cycles
{
if (string.charAt(i+1) == '#' && string.charAt(i - 1) != '1')
{
}
}
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