The ensureCapacity(int minimumCapacity) method of StringBuilder class helps us to ensures the capacity is at least equal to the specified minimumCapacity passed as the parameter to the method.
- If the current capacity of StringBuilder is less than the argument minimumCapacity, then a new internal array is allocated with greater capacity.
- If the minimumCapacity argument is greater than twice the old capacity, plus 2 then new capacity is equal to minimumCapacity else new capacity is equal to twice the old capacity, plus 2.
- If the minimumCapacity argument passed as parameter is not-positive, this method takes no action.
Syntax:
public void ensureCapacity(int minimumCapacity)
Parameters: This method accepts one parameter minimumCapacity represents the minimum desired capacity you want.
Return Value: This method do not return anything.
Below programs demonstrate the ensureCapacity() method of StringBuilder Class:
Example 1:
In this program minimumCapacity argument which is equal to 18 is less than twice the old capacity, plus 2 which is equal to 34 then new capacity is equal to 34.
// Java program to demonstrate// the ensureCapacity() Method.  class GFG {    public static void main(String[] args)    {        // create a StringBuilder object        StringBuilder str = new StringBuilder();          // print string capacity        System.out.println("Before ensureCapacity "                           + "method capacity = "                           + str.capacity());          // apply ensureCapacity()        str.ensureCapacity(18);          // print string capacity        System.out.println("After ensureCapacity"                           + " method capacity = "                           + str.capacity());    }} |
Output:
Before ensureCapacity method capacity = 16 After ensureCapacity method capacity = 34
Example 2:
In this program minimumCapacity argument which is equal to 44 is greater than twice the old capacity, plus 2 which is equal to 34 then new capacity is equal to 34.
// Java program to demonstrate// the ensureCapacity() Method.  class GFG {    public static void main(String[] args)    {          // create a StringBuilder object        StringBuilder str = new StringBuilder();          // print string capacity        System.out.println("Before ensureCapacity"                           + " method capacity = "                           + str.capacity());          // apply ensureCapacity()        str.ensureCapacity(44);          // print string capacity        System.out.println("After ensureCapacity"                           + " method capacity = "                           + str.capacity());    }} |
Output:
Before ensureCapacity method capacity = 16 After ensureCapacity method capacity = 44
Reference:
https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuilder.html#ensureCapacity(int)
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