Making strings from strings

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When a string is made from another string, it is called a substring.

Java provides two methods to make substrings: substring(int beginIndex) and substring(int beginIndex, int endIndex).

Called on: the "parent" string


  • the index at which to begin searching
  • (optional) the index at which to stop searching. Defaults to the string's last index.

Returns: the substring between beginIndex and endIndex or the word's end.


String word = "racecar";
word.substring(0);              // "racecar"
word;                           // still "racecar"
word.substring(4);              // "car"
word;                           // still "racecar"
word.substring(0, 4);           // "race"
word;                           // "racecar"

Strings can't be modified, so calling (for example) word.substring(4); above creates and returns a new string ("car") but doesn't change the original string ("racecar").

Saving substrings

To save the substring that gets returned, assign it to a variable:

String jewels = "Diamonds, rubies, and emeralds.";
String shorter = jewels.substring(10,16);
jewels;                             // "Diamonds, rubies, and emeralds.";
shorter;                            // "rubies"

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