JDK 9 doesn't recognize a slash leading file URI as a valid classpath in Windows.

Testcase & Reproduction Instructions
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%JDK9%\bin\javac C:\hello\Hello.java
%JDK9%\bin\jar cvf C:\hello.jar C:¥hello

%JDK9%\bin\java -cp C:\hello.jar Hello
Hello

%JDK9%\bin\java -cp C:/ hello.jar Hello
Hello

%JDK9%\bin\java -cp /C:/ hello.jar Hello
Error: Could not find or load main class hello.Hello
Caused by: java.lang.ClassNotFoundException: hello.Hello

%JDK8%\bin\java -cp /C:/ hello.jar Hello
Hello