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I've been looking at the implementation and I don't understand why there is an offset. I assume it is important.
I'm taking an Algorithms course taught by Sedgewick, and we're talking about Strings now. In lecture he briefly discussed the String implementation, but he doesn't go over why there is an offset (Note, if lectures were not online, I would definitely have asked).
It seems when one makes a String that within the implementation, it is given an offset, and I can't seem to understand why one is needed. Even for substring purposes I don't quite follow why you would have an offset. For example, apparently if you create a string "David", it is really ['X', 'X', 'D', 'a', 'v', 'i', 'd', 'X'], or something of that nature, where it is offset by the 'X's. Why is this?
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The offset is the first index of the storage that is used. Internally a String is represented as a sequence of chars in an array. This is the first char to use from the array. It has been introducted because some operations like substring create a new String using the original char array using a different offset.
String concatenation is implemented through the StringBuilder (or StringBuffer ) class and its append method. String conversions are implemented through the method toString , defined by Object and inherited by all classes in Java.
The idea is to use the deleteCharAt() method of StringBuilder class to remove first and the last character of a string. The deleteCharAt() method accepts a parameter as an index of the character you want to remove. Remove last character of a string using sb. deleteCharAt(str.
We can use string replace() function to replace a character with a new character. If we provide an empty string as the second argument, then the character will get removed from the string.
This can be useful in cases where strings need to be derived from another longer string, akin to substring().
In this case the same (immutable) backing array may be used, while adjusting the offset and length, to save memory and optimize performance.
This is no longer the case in JDK7.
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