Max size for StringBuffer

Question

Why would the StringBuffer have a limit on its size?

I went through some of the links : http://www.coderanch.com/t/540346/java/java/maximum-size-hold-S

Answer 1

if you are getting anywhere near 2^31 characters in your buffer you are doing it wrong and you would have run out of memory long ago.

Answer 2

Answer is different based on System architecture.

This old machine when I posted answer on 2012

Max Length of characters = 37748734

Java Version : 1.6.0_35

OS : Windows 7

System Architecture : 32bits (x86)

RAM : 2 GB

Processor : Pentium Dual Core E5800 3.20GHz

On 2016

Max Length of characters = 301989886

Java Version : 1.8

OS : Ubuntu 14 LTE and Windows 7

System Architecture : 64bits (x86_64)

RAM : 8 GB

Processor : Intel(R) Core(TM) i3-4130 CPU @ 3.40GHz

Run This program your self

        StringBuffer strbTest = new StringBuffer();
        long len = 0;
        try {
            System.out.println("Wait.... til number not generated.");

            while(true) {
                strbTest.append("a");
                len++;
            }
        } catch (OutOfMemoryError e) {
            System.out.println("Max length on your system is "+len);
            System.out.println("Error");
        }
        System.out.println("End");

Output

Max length on your system is 37748734

Answer 3

StringBuffer uses a char[].
In Java an array can be indexed only via an integer which means the highest value the index of the array can be is Integer.MAX_VALUE - 1 (i.e. 2^31 - 1). Which means that the size of an array in Java can not be larger than Integer.MAX_VALUE

Answer 4

because stringbuffer internally uses an array and the maximum number of elements an array can accommodate is 2^31-1 if you increment after reaching this it will go to negative and throws the error