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StringBuilder

StringBuilder

Scala strings are immutable. Sometimes we need a mutable string, typically because we want to build up a long string from small pieces, for instance in a loop. The StringBuilder class is useful as a mutable string that can grow efficiently (it is implemented using the doubling strategy). A StringBuilder object B can mostly be used like a string, but it is mutable, and you can append to it:

• B += ch appends the character ch;
• B ++= s appends the string s;
• B.append(n) appends the string representation of the number n (which can be any number type such as Int, Double, Long, etc.);
• B.clear() resets the contents to the empty string;
• B.delete(i, j) deletes characters from index i (inclusive) until j (exclusive);
• B.insert(i, s) inserts the string s at index i;
• B.toString returns the contents as a normal, immutable string.

In addition, StringBuilder provides all the common methods of sequences—a StringBuilder is a sequence of Char elements.

For instance:

scala> val B = new StringBuilder
B: StringBuilder = 
scala> B ++= "Hello"
res0: B.type = Hello
scala> B += ' '
res1: B.type = Hello 
scala> B ++= "World"
res2: B.type = Hello World
scala> B.delete(1,2)
res3: StringBuilder = Hllo World
scala> B.insert(5, "CS206 ")
res4: StringBuilder = Hllo CS206 World
scala> B(1) = 'e'
scala> B
res5: StringBuilder = Helo CS206 World
scala> B.toString
res6: java.lang.String = Helo CS206 World