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 returns do not return anything.

Below programs demonstrate the ensureCapacity() method of StringBuffer Class



Example 1:

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// 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());
    }
}

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Output:

Before ensureCapacity method capacity = 16
After ensureCapacity method capacity = 34

Example 2:

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// 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());
    }
}

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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)

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