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StringBuffer ensureCapacity() method in Java with Examples

Last Updated : 28 Dec, 2022
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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(&quot;Before ensureCapacity &quot;
                           + &quot;method capacity = &quot;
                           + str.capacity());

        // apply ensureCapacity()
        str.ensureCapacity(18);

        // print string capacity
        System.out.println(&quot;After ensureCapacity&quot;
                           + &quot; method capacity = &quot;
                           + 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(&quot;Geeks For Geeks&quot;);

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

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

        // print string capacity
        System.out.println(&quot;After ensureCapacity&quot;
                           + &quot; method capacity = &quot;
                           + 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)


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AmanSingh2210
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