Example of StringBuilder by ensureCapacity() method in java.

class string27
{
public static void main(String args[])
{
StringBuilder sb=new StringBuilder();
System.out.println(sb.capacity());//default 16

sb.append("Hello");
System.out.println(sb.capacity());//now 16

sb.append("java is my favourite language");
System.out.println(sb.capacity());//now (16*2)+2=34 i.e (oldcapacity*2)+2

sb.ensureCapacity(10);//now no change
System.out.println(sb.capacity());//now 34

sb.ensureCapacity(50);//now (34*2)+2
System.out.println(sb.capacity());//now 70
}
}

Output: