[#1815] add example application

src/test/java/picocli/Issue1815Group.java

@@ -0,0 +1,84 @@
+package picocli;
+
+import picocli.CommandLine.ArgGroup;
+import picocli.CommandLine.Command;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Callable;
+
+// https://github.com/remkop/picocli/issues/1815
+public class Issue1815Group {
+    @Command(name = "groups", mixinStandardHelpOptions = true,
+        description = "groups fun")
+    static class CmdTest implements Callable<Integer> {
+
+        @ArgGroup(validate = false, heading = "GROUP A%n", multiplicity = "0..1")
+        private List<GroupA> a = new ArrayList<GroupA>();
+
+//        @ArgGroup(validate = true, exclusive = false, heading = "GROUP A%n", multiplicity = "0..1")
+//        private GroupA a = new GroupA();
+
+        @ArgGroup(validate = false, heading = "GROUP B%n")
+        private GroupB b = new GroupB();
+
+        public Integer call() {
+            System.out.println(a);
+            System.out.println(b);
+            return 0;
+        }
+
+        public static void main(String[] args) {
+            int exitCode = new CommandLine(new CmdTest()).execute(args);
+            System.exit(exitCode);
+        }
+    }
+    static class GroupA {
+        @CommandLine.Option(
+            names = {"--a-str"},
+            paramLabel = "<NETWORK>",
+            //required = true,
+            arity = "1")
+        private String str = null;
+
+        @CommandLine.Option(
+            names = {"--a-bool"},
+            paramLabel = "<BOOLEAN>",
+            arity = "1",
+            //required = true,
+            fallbackValue = "true")
+        private boolean bool = false;
+
+        public GroupA() {
+        }
+
+        @Override
+        public String toString() {
+            final StringBuilder sb = new StringBuilder("GroupA{");
+            sb.append("str='").append(str).append('\'');
+            sb.append(", bool=").append(bool);
+            sb.append('}');
+            return sb.toString();
+        }
+    }
+    static class GroupB {
+        @CommandLine.Option(
+            names = {"--b-bool"},
+            paramLabel = "<BOOLEAN>",
+            showDefaultValue = CommandLine.Help.Visibility.ALWAYS,
+            fallbackValue = "true",
+            arity = "1")
+        private boolean b = false;
+
+        public GroupB() {
+        }
+
+        @Override
+        public String toString() {
+            final StringBuilder sb = new StringBuilder("GroupB{");
+            sb.append("b=").append(b);
+            sb.append('}');
+            return sb.toString();
+        }
+    }
+}