StringBuffer ensureCapacity() method in Java with Examples

The ensureCapacity() method of StringBuffer class ensures the capacity to at least equal to the specified minimumCapacity.

• If the current capacity of StringBuffer < the argument minimumCapacity, then a new internal array is allocated with greater capacity.
• If the minimumCapacity argument > 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 < 0, this method takes no action.

Syntax:

public void ensureCapacity(int minimumCapacity)

Parameters: This method takes one parameter minimumCapacity which is the minimum desired capacity. Return Value: This method do not return anything. Below programs demonstrate the ensureCapacity() method of StringBuffer Class Example 1:

Java

// Java program to demonstrate
// the ensureCapacity() Method.

class GFG {
    public static void main(String[] args)
    {

        // create a StringBuffer object
        StringBuffer str = new StringBuffer();

        // 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:

Java

// Java program to demonstrate
// the ensureCapacity() Method.

class GFG {
    public static void main(String[] args)
    {

        // create a StringBuffer object
        StringBuffer
            str
            = new StringBuffer("Geeks For Geeks");

        // print string capacity
        System.out.println("Before ensureCapacity "
                           + "method capacity = "
                           + str.capacity());

        // apply ensureCapacity()
        str.ensureCapacity(42);

        // print string capacity
        System.out.println("After ensureCapacity"
                           + " method capacity = "
                           + str.capacity());
    }
}

Output:

Before ensureCapacity method capacity = 31
After ensureCapacity method capacity = 64

References: https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuffer.html#ensureCapacity(int)