add JarLister

src/main/java/org/cobbzilla/util/io/JarLister.java

@@ -0,0 +1,45 @@
+package org.cobbzilla.util.io;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.experimental.Accessors;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.function.Function;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.regex.Pattern;
+
+@AllArgsConstructor @Accessors(chain=true)
+public class JarLister {
+
+    @Getter private final JarFile jar;
+    @Getter private final Pattern pattern;
+    @Getter private final Function<String, String> nameMapper;
+
+    public JarLister (File jar, String pattern, Function<String, String> nameMapper) throws IOException {
+        this.jar = new JarFile(jar);
+        this.pattern = Pattern.compile(pattern);
+        this.nameMapper = nameMapper;
+    }
+
+    public JarLister (File jar, String pattern) throws IOException { this(jar, pattern, Function.identity()); }
+
+    public List<String> list() {
+        final Enumeration<JarEntry> entries = jar.entries();
+        final List<String> found = new ArrayList<>();
+        while (entries.hasMoreElements()) {
+            final JarEntry jarEntry = entries.nextElement();
+            final String name = jarEntry.getName();
+            if (pattern.matcher(name).matches()) {
+                found.add(nameMapper.apply(name));
+            }
+        }
+        return found;
+    }
+
+}