Hello. I found suspicious check in all 4 JDK implementations of java.nio.file.FileSystem#getPathMatcher
https://github.com/openjdk/jdk/blob/8c1870521815a24fd12480e73450c2201542a442/src/java.base/share/classes/jdk/internal/jrtfs/JrtFileSystem.java#L178 https://github.com/openjdk/jdk/blob/8c1870521815a24fd12480e73450c2201542a442/src/java.base/unix/classes/sun/nio/fs/UnixFileSystem.java#L285 https://github.com/openjdk/jdk/blob/8c1870521815a24fd12480e73450c2201542a442/src/java.base/windows/classes/sun/nio/fs/WindowsFileSystem.java#L264 https://github.com/openjdk/jdk/blob/8c1870521815a24fd12480e73450c2201542a442/src/jdk.zipfs/share/classes/jdk/nio/zipfs/ZipFileSystem.java#L444 public PathMatcher getPathMatcher(String syntaxAndInput) { int pos = syntaxAndInput.indexOf(':'); if (pos <= 0 || pos == syntaxAndInput.length()) { throw new IllegalArgumentException(); } Variable 'pos' is the result of the 'String.indexOf' method call. Then variable 'pos' is compared with 'length()' of the string with ==. But the maximum possible returned value of String.indexOf() is 'length()-1'. It means check 'pos == syntaxAndInput.length()' will always be 'false'. Andrey Turbanov
