question: @ NotNull public static String appendToPathEnvVar ( @ Nullable String source , @ NotNull String value ) { if ( StringUtil . isEmpty ( source ) ) return value ; Set < String > paths = Sets . newHashSet ( source . split ( File . pathSeparator ) ) ; return ! paths . contains ( value ) ? source + File . pathSeparator + value : source ; }
target:  Appends a value to the end os a path-like environment variable, using system-dependent path separator.