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A question relating to performance considerations for String.substring. Prior to Java 1.7.0_06, the String.substring() method returned a new String object that shared the same underlying char array as its parents but with different offset and length. To avoid keeping a very large string in memory when only a small substring was needed to be kept, programmers used to write code like this:
s = new String(queryReturningHugeHugeString().substring(0,3));
From 1.7.0_06 onwards, it has not been necessary to create a new String because in Oracle's implementation of String, substrings no longer share their underlying char array.
My question is: can we rely on Oracle (and other vendors) not going back to char[] sharing in some future release, and simply do s = s.substr(...), or should we explicitly create a new String just in case some future release of the JRE starts using a sharing implementation again?
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The substring() method extracts characters, between two indices (positions), from a string, and returns the substring. The substring() method extracts characters from start to end (exclusive).
Deleting the first character : Strings in Java start at index 0, i.e., the first character is 0 indexed. If you need to remove the first character, use substring(1). This returns the substring without the initial character, which equals deleting the first character.
You can use contains(), indexOf() and lastIndexOf() method to check if one String contains another String in Java or not. If a String contains another String then it's known as a substring. The indexOf() method accepts a String and returns the starting position of the string if it exists, otherwise, it will return -1.
The actual representation of the String is an internal implementation detail, so you can never be sure. However according to public talks of Oracle engineers (most notably @shipilev) it's very unlikely that it will be changed back. This was done not only to fight with possible memory leak, but also to simplify the String internals. With simpler strings it's easier to implement many optimization techniques like String deduplication or Compact Strings.
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