Clearing a string buffer/builder after loop

How do you clear the string buffer in Java after a loop so the next iteration uses a clear string buffer?

Solution 1:

One option is to use the delete method as follows:

StringBuffer sb = new StringBuffer();
for (int n = 0; n < 10; n++) {
   sb.append("a");

   // This will clear the buffer
   sb.delete(0, sb.length());
}

Another option (bit cleaner) uses setLength(int len):

sb.setLength(0);

See Javadoc for more info:

Solution 2:

The easiest way to reuse the StringBuffer is to use the method setLength()

public void setLength(int newLength)

You may have the case like

StringBuffer sb = new StringBuffer("HelloWorld");
// after many iterations and manipulations
sb.setLength(0);
// reuse sb

Solution 3:

You have two options:

Either use:

sb.setLength(0);  // It will just discard the previous data, which will be garbage collected later.  

Or use:

sb.delete(0, sb.length());  // A bit slower as it is used to delete sub sequence.  

NOTE

Avoid declaring StringBuffer or StringBuilder objects within the loop else it will create new objects with each iteration. Creating of objects requires system resources, space and also takes time. So for long run, avoid declaring them within a loop if possible.

Solution 4:

I suggest creating a new StringBuffer (or even better, StringBuilder) for each iteration. The performance difference is really negligible, but your code will be shorter and simpler.

Solution 5:

public void clear(StringBuilder s) {
    s.setLength(0);
}

Usage:

StringBuilder v = new StringBuilder();
clear(v);

for readability, I think this is the best solution.