How to increase Java Heap size in aws Lambda?

I am using AWS SDK http://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/s3/package-summary.html

to program a data processing in AWS Lambda

encountered the error

    {
  "errorMessage": "Java heap space",
  "errorType": "java.lang.OutOfMemoryError",
  "stackTrace": [
    "java.util.Arrays.copyOf(Arrays.java:3332)",
    "java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:137)",
    "java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:121)",
    "java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:569)",
    "java.lang.StringBuffer.append(StringBuffer.java:369)",
    "java.io.StringWriter.write(StringWriter.java:94)",
    "org.apache.commons.io.IOUtils.copyLarge(IOUtils.java:1129)",
    "org.apache.commons.io.IOUtils.copy(IOUtils.java:1104)",
    "org.apache.commons.io.IOUtils.copy(IOUtils.java:1050)",
    "org.apache.commons.io.IOUtils.copy(IOUtils.java:1075)",
    "org.apache.commons.io.IOUtils.toString(IOUtils.java:382)",
    "example.Hello.myHandler(Hello.java:47)",
    "sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)",
    "sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)",
    "sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)",
    "java.lang.reflect.Method.invoke(Method.java:497)"
  ]
}

I want to solve this by increase heap size programmatically

The code caused this problem is

AmazonS3 s3Client = new AmazonS3Client();
S3Object s3Object = s3Client.getObject(new GetObjectRequest(srcBucket, srcKey));
InputStream objectData = s3Object.getObjectContent();

// transfer data into JSON
String theString = IOUtils.toString(objectData, null);

The object I am extracting is about 300MB. and Configuration of Lambda

Memory: 1024 MB

You will be better off using Gson or Jackson APIs to parse your Json object rather than working with Lambda limitation.

something like that can help you started

AmazonS3 s3Client = new AmazonS3Client();
S3Object s3Object = s3Client.getObject(new GetObjectRequest(srcBucket, srcKey));
InputStream objectData = s3Object.getObjectContent();

// transfer data into JSON
JsonFactory jsonfactory = new JsonFactory(); 
JsonParser parser = jsonfactory.createJsonParser(objectData); 

// starting parsing of JSON String 
while (parser.nextToken() != JsonToken.END_OBJECT) { 
    // do what you need to do
}