"I [...] noticed that sun.net.www.ParseUtil.encodePath(String, boolean) usually had nothing useful to do but still made three copies of the string passed in anyway (two char arrays to work on, and the String returned)."

http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-December/045180.html

Scanning the string to see if there are characters that actually need encoding may reduce allocation for applications scanning many jars for resources. However, since file paths on Windows might mean always transforming the String it's important not to regress the "slow" path.