But Kotlin is the fastest-growing in percentage terms, and is likely to continue its quick growth due to Google’s preference for it for Android apps, SlashData said its latest half-year developer report.
Some 3 million developers began using the language from the fourth quarter of 2017 to the fourth quarter of 2019, the biggest growth in absolute terms of any language.
That includes both entry-level programmers and experienced developers, with the language popular for web applications, cloud services and extensions for third-party environments.
Python and Java have added nearly 4 million developers combined over the past two years, with Python adding 2.2 million net new developers in 2018 and surpassing Java in popularity.
In 2019 Python grew less quickly, but remains the second most widely used language, in part because of the rise of data science and machine learning.
Some 75 percent of machine learning developers and data scientists said they used Python, compared to less than 20 percent for R, a specialised programming language for statistical computing and graphics.
Java is popular in mobile computing, particularly Android apps, and in backend development, and it continues to grow steadily, adding more than half a million developers in 2017, 2018 and 2019, for a total of more than 8 million.
SlashData estimates there are 8.4 million Python and 8.2 million Java developers.
But Kotlin is the fastest-growing language in percentage terms, with its developer base nearly doubling in size in the past two years, from 1.1 million in the fourth quarter of 2017 to 2 million in the same quarter of last year.
“Given that Google has made Kotlin its preferred language for Android development, we can only expect this growth to continue,” SlashData said in the study.
The firm added it sees Kotlin “becoming a core language in mobile development”.
C++, C#, Visual tools, Kotlin, Swift, Go, Ruby and Objective C also all have more than one million users, with Rust used by 600,000 developers and Lua by 500,000.
Developers using Swift declined year-to-year in 2019 to 2 million, and Objective C was also down to 1.2 million.
Some 59 percent of developers said they contribute to open source software, one-third of whom are under the age of 24, SlashData found.
The firm found that 29 percent of these were looking to improve their coding skills, with 26 saying it was because they believe in the benefits of open source software. Only 3 percent were paid for their open source work.
Just under half of developers, at 44 percent, said they expect companies to support and contribute to open source projects, although 39 percent said they don’t expect companies to build products and services on open source software.
“Open source software is a central part of the developer world,” SlashData said in the study.
It added that the collaborative nature of open source “embodies the widely held values of sharing code, knowledge, and best practices which is core to developer culture”.
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