Styling: support specifying multiple style classes in single string

flatlaf-core/src/main/java/com/formdev/flatlaf/FlatClientProperties.java

@@ -146,8 +146,8 @@ public interface FlatClientProperties
 	String STYLE = "FlatLaf.style";
 
 	/**
-	 * Specifies the style class(es) of a component as String
+	 * Specifies the style class(es) of a component as String (single class or multiple classes separated by space characters)
-	 * or as {@link java.util.List}<String>.
+	 * or as {@code String[]} or {@link java.util.List}<String> (multiple classes).
 	 * <p>
 	 * The style rules must be defined in UI defaults either as strings (in CSS syntax)
 	 * or as {@link java.util.Map}&lt;String, Object&gt; (with binary values).

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatStylingSupport.java

@@ -127,7 +127,7 @@ public class FlatStylingSupport
 	 *     UIManager.get( "[style]Button.foo" ) );
 	 * }</pre>
 	 *
-	 * @param styleClass the style class(es) either as string (single class)
+	 * @param styleClass the style class(es) either as string (single class or multiple classes separated by space characters)
 	 *                   or as {@code String[]} or {@link java.util.List}&lt;String&gt; (multiple classes)
 	 * @param type the type of the component
 	 * @return the styles
@@ -136,8 +136,11 @@ public class FlatStylingSupport
 		if( styleClass == null )
 			return null;
 
+		if( styleClass instanceof String && ((String)styleClass).indexOf( ' ' ) >= 0 )
+			styleClass = StringUtils.split( (String) styleClass, ' ', true, true );
+
 		if( styleClass instanceof String )
-			return getStyleForClass( (String) styleClass, type );
+			return getStyleForClass( ((String)styleClass).trim(), type );
 		else if( styleClass instanceof String[] ) {
 			Object style = null;
 			for( String cls : (String[]) styleClass )

flatlaf-core/src/main/java/com/formdev/flatlaf/util/StringUtils.java

@@ -17,6 +17,7 @@
 package com.formdev.flatlaf.util;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -46,16 +47,50 @@ public class StringUtils
 	}
 
 	public static List<String> split( String str, char delim ) {
-		ArrayList<String> strs = new ArrayList<>();
+		return split( str, delim, false, false );
+	}
+
+	/**
+	 * Splits a string at the specified delimiter.
+	 * If trimming is enabled, then leading and trailing whitespace characters are removed.
+	 * If excludeEmpty is {@code true}, then only non-empty strings are returned.
+	 *
+	 * @since 2
+	 */
+	public static List<String> split( String str, char delim, boolean trim, boolean excludeEmpty ) {
 		int delimIndex = str.indexOf( delim );
+		if( delimIndex < 0 ) {
+			if( trim )
+				str = str.trim();
+			return !excludeEmpty || !str.isEmpty()
+				? Collections.singletonList( str )
+				: Collections.emptyList();
+		}
+
+		ArrayList<String> strs = new ArrayList<>();
 		int index = 0;
 		while( delimIndex >= 0 ) {
-			strs.add( str.substring( index, delimIndex ) );
+			add( strs, str, index, delimIndex, trim, excludeEmpty );
 			index = delimIndex + 1;
 			delimIndex = str.indexOf( delim, index );
 		}
-		strs.add( str.substring( index ) );
+		add( strs, str, index, str.length(), trim, excludeEmpty );
 
 		return strs;
 	}
+
+	private static void add( List<String> strs, String str, int begin, int end, boolean trim, boolean excludeEmpty ) {
+		if( trim ) {
+			// skip leading whitespace
+			while( begin < end && str.charAt( begin ) <= ' ' )
+				begin++;
+
+			// skip trailing whitespace
+			while( begin < end && str.charAt( end - 1 ) <= ' ' )
+				end--;
+		}
+
+		if( !excludeEmpty || end > begin )
+			strs.add( str.substring( begin, end ) );
+	}
 }

flatlaf-core/src/test/java/com/formdev/flatlaf/ui/TestFlatStyleClasses.java

@@ -19,6 +19,7 @@ package com.formdev.flatlaf.ui;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import java.awt.Color;
 import java.awt.Dimension;
+import java.util.Arrays;
 import javax.swing.*;
 import javax.swing.table.JTableHeader;
 import org.junit.jupiter.api.AfterAll;
@@ -114,10 +115,25 @@ public class TestFlatStyleClasses
 
 		assertEquals(
 			FlatStylingSupport.concatStyles( BUTTON_PRIMARY, SECONDARY ),
-			FlatStylingSupport.getStyleForClasses( new String[] { "primary", "secondary" }, "Button" ) );
+			FlatStylingSupport.getStyleForClasses( "primary secondary", "Button" ) );
+		assertEquals(
+			FlatStylingSupport.concatStyles( SECONDARY, BUTTON_PRIMARY ),
+			FlatStylingSupport.getStyleForClasses( "secondary primary", "Button" ) );
+
+		// String
+		assertEquals(
+			FlatStylingSupport.concatStyles( SECONDARY, BUTTON_PRIMARY ),
+			FlatStylingSupport.getStyleForClasses( "  secondary    primary  bla blu  ", "Button" ) );
+
+		// String[]
 		assertEquals(
 			FlatStylingSupport.concatStyles( SECONDARY, BUTTON_PRIMARY ),
 			FlatStylingSupport.getStyleForClasses( new String[] { "secondary", "primary" }, "Button" ) );
+
+		// List<String>
+		assertEquals(
+			FlatStylingSupport.concatStyles( SECONDARY, BUTTON_PRIMARY ),
+			FlatStylingSupport.getStyleForClasses( Arrays.asList( "secondary", "primary" ), "Button" ) );
 	}
 
 	@Test
@@ -132,7 +148,7 @@ public class TestFlatStyleClasses
 	@Test
 	void apply2() {
 		JButton c = new JButton();
-		c.putClientProperty( FlatClientProperties.STYLE_CLASS, new String[] { "primary", "secondary" } );
+		c.putClientProperty( FlatClientProperties.STYLE_CLASS, "primary secondary" );
 
 		assertEquals( new Color( 0x00ff88 ), c.getBackground() );
 		assertEquals( Color.white, c.getForeground() );
@@ -141,7 +157,7 @@ public class TestFlatStyleClasses
 	@Test
 	void apply3() {
 		JButton c = new JButton();
-		c.putClientProperty( FlatClientProperties.STYLE_CLASS, new String[] { "secondary", "primary" } );
+		c.putClientProperty( FlatClientProperties.STYLE_CLASS, "secondary primary" );
 
 		assertEquals( new Color( 0x0088ff ), c.getBackground() );
 		assertEquals( Color.white, c.getForeground() );

flatlaf-core/src/test/java/com/formdev/flatlaf/util/TestStringUtils.java

@@ -0,0 +1,198 @@
+/*
+ * Copyright 2021 FormDev Software GmbH
+ *
+ * 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 com.formdev.flatlaf.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import java.util.Arrays;
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author Karl Tauber
+ */
+public class TestStringUtils
+{
+	@Test
+	void split() {
+		// empty
+		assertEquals(
+			Arrays.asList( "" ),
+			StringUtils.split( "", ',' ) );
+
+		// not empty
+		assertEquals(
+			Arrays.asList( "a" ),
+			StringUtils.split( "a", ',' ) );
+		assertEquals(
+			Arrays.asList( "a", "b" ),
+			StringUtils.split( "a,b", ',' ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a,b,c", ',' ) );
+
+		// empty parts
+		assertEquals(
+			Arrays.asList( "", "b", "c" ),
+			StringUtils.split( ",b,c", ',' ) );
+		assertEquals(
+			Arrays.asList( "a", "", "c" ),
+			StringUtils.split( "a,,c", ',' ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "" ),
+			StringUtils.split( "a,b,", ',' ) );
+
+		// parts with leading/trailing spaces
+		assertEquals(
+			Arrays.asList( "a", " b", " c" ),
+			StringUtils.split( "a, b, c", ',' ) );
+		assertEquals(
+			Arrays.asList( " a", "b", "c " ),
+			StringUtils.split( " a,b,c ", ',' ) );
+		assertEquals(
+			Arrays.asList( "  a", "  b  ", "c  " ),
+			StringUtils.split( "  a,  b  ,c  ", ',' ) );
+
+		// space delimiter
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a b c", ' ' ) );
+		assertEquals(
+			Arrays.asList( "a", "", "", "b", "", "c" ),
+			StringUtils.split( "a   b  c", ' ' ) );
+
+		// new line delimiter
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a\nb\nc", '\n' ) );
+		assertEquals(
+			Arrays.asList( "a", "", "", "b", "", "c" ),
+			StringUtils.split( "a\n\n\nb\n\nc", '\n' ) );
+	}
+
+	@Test
+	void splitTrim() {
+		// empty
+		assertEquals(
+			Arrays.asList( "" ),
+			StringUtils.split( "", ',', true, false ) );
+
+		// not empty
+		assertEquals(
+			Arrays.asList( "a" ),
+			StringUtils.split( "a", ',', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "b" ),
+			StringUtils.split( "a,b", ',', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a,b,c", ',', true, false ) );
+
+		// empty parts
+		assertEquals(
+			Arrays.asList( "", "b", "c" ),
+			StringUtils.split( ",b,c", ',', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "", "c" ),
+			StringUtils.split( "a,,c", ',', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "" ),
+			StringUtils.split( "a,b,", ',', true, false ) );
+
+		// parts with leading/trailing spaces
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a, b, c", ',', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( " a,b,c ", ',', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "  a,  b  ,c  ", ',', true, false ) );
+
+		// space delimiter
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a b c", ' ', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "", "", "b", "", "c" ),
+			StringUtils.split( "a   b  c", ' ', true, false ) );
+
+		// new line delimiter
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a\nb\nc", '\n', true, false ) );
+		assertEquals(
+			Arrays.asList( "a", "", "", "b", "", "c" ),
+			StringUtils.split( "a\n\n\nb\n\nc", '\n', true, false ) );
+	}
+
+	@Test
+	void splitTrimAndExcludeEmpty() {
+		// empty
+		assertEquals(
+			Arrays.asList(),
+			StringUtils.split( "", ',', true, true ) );
+
+		// not empty
+		assertEquals(
+			Arrays.asList( "a" ),
+			StringUtils.split( "a", ',', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "b" ),
+			StringUtils.split( "a,b", ',', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a,b,c", ',', true, true ) );
+
+		// empty parts
+		assertEquals(
+			Arrays.asList( "b", "c" ),
+			StringUtils.split( ",b,c", ',', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "c" ),
+			StringUtils.split( "a,,c", ',', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "b" ),
+			StringUtils.split( "a,b,", ',', true, true ) );
+
+		// parts with leading/trailing spaces
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a, b, c", ',', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( " a,b,c ", ',', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "  a,  b  ,c  ", ',', true, true ) );
+
+		// space delimiter
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a b c", ' ', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a   b  c", ' ', true, true ) );
+
+		// new line delimiter
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a\nb\nc", '\n', true, true ) );
+		assertEquals(
+			Arrays.asList( "a", "b", "c" ),
+			StringUtils.split( "a\n\n\nb\n\nc", '\n', true, true ) );
+	}
+}