Java: Add Guard Classes for checking OS

java/ql/test/library-tests/os/Test.java

@@ -0,0 +1,34 @@
+import java.nio.file.FileSystems;
+import java.nio.file.Path;
+
+public class Test {
+    void test() {
+        if (System.getProperty("os.name").contains("Windows")) {
+            
+        }
+
+        if (System.getProperty("os.name").toLowerCase().contains("windows")) {
+            
+        }
+
+        if (System.getProperty("os.name").contains("Linux")) {
+            
+        }
+
+        if (System.getProperty("os.name").contains("Mac OS X")) {
+            
+        }
+
+        if (System.getProperty("os.name").toLowerCase().contains("mac")) {
+            
+        }
+
+        if (Path.of("whatever").getFileSystem().supportedFileAttributeViews().contains("posix")) {
+
+        }
+
+        if (FileSystems.getDefault().supportedFileAttributeViews().contains("posix")) {
+
+        }
+    }
+}

java/ql/test/library-tests/os/unix-test.expected

@@ -0,0 +1,5 @@
+| Test.java:14:13:14:59 | contains(...) |
+| Test.java:18:13:18:62 | contains(...) |
+| Test.java:22:13:22:71 | contains(...) |
+| Test.java:26:13:26:95 | contains(...) |
+| Test.java:30:13:30:84 | contains(...) |

java/ql/test/library-tests/os/unix-test.ql

@@ -0,0 +1,5 @@
+import default
+import semmle.code.java.os.OSCheck
+
+from IsUnixGuard isUnix
+select isUnix

java/ql/test/library-tests/os/windows-test.expected

@@ -0,0 +1,2 @@
+| Test.java:6:13:6:61 | contains(...) |
+| Test.java:10:13:10:75 | contains(...) |

java/ql/test/library-tests/os/windows-test.ql

@@ -0,0 +1,5 @@
+import default
+import semmle.code.java.os.OSCheck
+
+from IsWindowsGuard isWindows
+select isWindows