Dependencies

<dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-math</artifactId>
            <version>3.6.1</version>
</dependency>

using common maths stats classes

double[] readList = new double[]{2.0,4.0};
DescriptiveStatistics statistics = new DescriptiveStatistics(readList);
Double max = statistics.getMax();