Extract table-building logic into TableUtils class

Author: ritvik

src/main/java/org/springframework/cli/command/RoleCommands.java

@@ -21,20 +21,15 @@
 import java.nio.file.Path;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.cli.SpringCliException;
 import org.springframework.cli.roles.RoleService;
+import org.springframework.cli.util.TableUtils;
 import org.springframework.cli.util.TerminalMessage;
 import org.springframework.shell.command.annotation.Command;
 import org.springframework.shell.command.annotation.Option;
-import org.springframework.shell.table.ArrayTableModel;
-import org.springframework.shell.table.BorderStyle;
 import org.springframework.shell.table.Table;
-import org.springframework.shell.table.TableBuilder;
-import org.springframework.shell.table.TableModel;
 import org.springframework.util.StringUtils;
 
 @Command(command = "role", group = "Role")
@@ -129,19 +124,7 @@ public void roleGet(@Option(description = "Property key", required = true) Strin
 	public Table roleList() {
 		File directory = this.roleService.getRolesVarPath();
 		List<String> rolesNames = this.roleService.getRoleNames(directory);
-		Stream<String[]> header = Stream.<String[]>of(new String[] { "Name" });
-		Stream<String[]> rows;
-		if (rolesNames != null) {
-			rows = rolesNames.stream().map(tr -> new String[] { tr });
-		}
-		else {
-			rows = Stream.empty();
-		}
-		List<String[]> allRows = rows.collect(Collectors.toList());
-		String[][] data = Stream.concat(header, allRows.stream()).toArray(String[][]::new);
-		TableModel model = new ArrayTableModel(data);
-		TableBuilder tableBuilder = new TableBuilder(model);
-		return tableBuilder.addFullBorder(BorderStyle.fancy_light).build();
+		return TableUtils.buildTable(rolesNames, "Name");
 	}
 
 	public RoleService getRoleService() {

src/main/java/org/springframework/cli/util/TableUtils.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cli.util;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+import org.springframework.shell.table.ArrayTableModel;
+import org.springframework.shell.table.BorderStyle;
+import org.springframework.shell.table.Table;
+import org.springframework.shell.table.TableBuilder;
+import org.springframework.shell.table.TableModel;
+
+/**
+ * Utility class for building tables to display data in the CLI.
+ */
+public final class TableUtils {
+
+	// Private constructor to prevent instantiation
+	private TableUtils() {
+		throw new AssertionError("Utility class - do not instantiate");
+	}
+
+	/**
+	 * Builds a table with a single-column layout for displaying a list of items.
+	 * @param data the list of items to display in the table
+	 * @param header the header for the table column
+	 * @return a formatted Table object
+	 */
+	public static Table buildTable(List<String> data, String header) {
+		Stream<String[]> headerStream = Stream.<String[]>of(new String[] { header });
+		Stream<String[]> rows = (data != null) ? data.stream().map(item -> new String[] { item }) : Stream.empty();
+		String[][] tableData = Stream.concat(headerStream, rows).toArray(String[][]::new);
+		TableModel model = new ArrayTableModel(tableData);
+		TableBuilder tableBuilder = new TableBuilder(model);
+		return tableBuilder.addFullBorder(BorderStyle.fancy_light).build();
+	}
+
+}