Item 51 - Beware the performance of string concatenation
From Effective Java 2/e by Joshua Bloch
Strings are immutable
Using the string concatenation operator repeatedly to concatenate n strings requires time quadratic in n.
User StringBuilder instead of String it self
// Inappropriate use of string concatenation - Performs horribly!
public String statement() {
String result = "";
for (int i = 0; i < numItems(); i++)
result += lineForItem(i); // String concatenation
return result;
}
public String statement() {
StringBuilder b = new StringBuilder(numItems() * LINE_WIDTH);
for (int i = 0; i < numItems(); i++)
b.append(lineForItem(i));
return b.toString();
}
Because the first method is quadratic in the number of items and the second is linear, the performance difference is even more dramatic for larger numbers of items.
