Use String#isEmpty()

Closes gh-1335
(cherry picked from commit 7d062df)

spring-beans/src/main/java/org/springframework/beans/PropertyMatches.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -150,10 +150,10 @@ public abstract class PropertyMatches {
 	 * @return the distance value
 	 */
 	private static int calculateStringDistance(String s1, String s2) {
-		if (s1.length() == 0) {
+		if (s1.isEmpty()) {
 			return s2.length();
 		}
-		if (s2.length() == 0) {
+		if (s2.isEmpty()) {
 			return s1.length();
 		}
 		int d[][] = new int[s1.length() + 1][s2.length() + 1];

spring-core/src/main/java/org/springframework/core/convert/support/StringToCharacterConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -28,7 +28,7 @@ final class StringToCharacterConverter implements Converter<String, Character> {
 
 	@Override
 	public Character convert(String source) {
-		if (source.length() == 0) {
+		if (source.isEmpty()) {
 			return null;
 		}
 		if (source.length() > 1) {

spring-core/src/main/java/org/springframework/core/convert/support/StringToEnumConverterFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -45,7 +45,7 @@ final class StringToEnumConverterFactory implements ConverterFactory<String, Enu
 
 		@Override
 		public T convert(String source) {
-			if (source.length() == 0) {
+			if (source.isEmpty()) {
 				// It's an empty enum identifier: reset the enum value to null.
 				return null;
 			}

spring-core/src/main/java/org/springframework/core/convert/support/StringToNumberConverterFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -56,7 +56,7 @@ final class StringToNumberConverterFactory implements ConverterFactory<String, N
 
 		@Override
 		public T convert(String source) {
-			if (source.length() == 0) {
+			if (source.isEmpty()) {
 				return null;
 			}
 			return NumberUtils.parseNumber(source, this.targetType);

spring-core/src/main/java/org/springframework/core/io/support/PathMatchingResourcePatternResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -833,7 +833,7 @@ public class PathMatchingResourcePatternResolver implements ResourcePatternResol
 		public PatternVirtualFileVisitor(String rootPath, String subPattern, PathMatcher pathMatcher) {
 			this.subPattern = subPattern;
 			this.pathMatcher = pathMatcher;
-			this.rootPath = (rootPath.length() == 0 || rootPath.endsWith("/") ? rootPath : rootPath + "/");
+			this.rootPath = (rootPath.isEmpty() || rootPath.endsWith("/") ? rootPath : rootPath + "/");
 		}
 
 		@Override

spring-core/src/main/java/org/springframework/util/Base64Utils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -159,7 +159,7 @@ public abstract class Base64Utils {
 		if (src == null) {
 			return null;
 		}
-		if (src.length() == 0) {
+		if (src.isEmpty()) {
 			return new byte[0];
 		}
 

spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java

@@ -243,7 +243,7 @@ public abstract class MimeTypeUtils {
 
 		int index = mimeType.indexOf(';');
 		String fullType = (index >= 0 ? mimeType.substring(0, index) : mimeType).trim();
-		if (fullType.length() == 0) {
+		if (fullType.isEmpty()) {
 			throw new InvalidMimeTypeException(mimeType, "'mimeType' must not be empty");
 		}
 

spring-core/src/main/java/org/springframework/util/StringUtils.java

@@ -371,7 +371,7 @@ public abstract class StringUtils {
 	 * @param sub string to search for. Return 0 if this is {@code null}.
 	 */
 	public static int countOccurrencesOf(String str, String sub) {
-		if (str == null || sub == null || str.length() == 0 || sub.length() == 0) {
+		if (!hasLength(str) || !hasLength(sub)) {
 			return 0;
 		}
 		int count = 0;
@@ -513,25 +513,23 @@ public abstract class StringUtils {
 	}
 
 	private static String changeFirstCharacterCase(String str, boolean capitalize) {
-		if (str == null || str.length() == 0) {
+		if (!hasLength(str)) {
 			return str;
 		}
-		else {
-			char baseChar = str.charAt(0);
-			char updatedChar;
-			if (capitalize) {
-				updatedChar = Character.toUpperCase(baseChar);
-			}
-			else {
-				updatedChar = Character.toLowerCase(baseChar);
-			}
-			if (baseChar == updatedChar) {
-				return str;
-			}
-			char[] chars = str.toCharArray();
-			chars[0] = updatedChar;
-			return new String(chars, 0, chars.length);
+		char baseChar = str.charAt(0);
+		char updatedChar;
+		if (capitalize) {
+			updatedChar = Character.toUpperCase(baseChar);
 		}
+		else {
+			updatedChar = Character.toLowerCase(baseChar);
+		}
+		if (baseChar == updatedChar) {
+			return str;
+		}
+		char[] chars = str.toCharArray();
+		chars[0] = updatedChar;
+		return new String(chars, 0, chars.length);
 	}
 
 	/**

spring-core/src/main/java/org/springframework/util/xml/AbstractStaxHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -223,8 +223,8 @@ abstract class AbstractStaxHandler implements ContentHandler, LexicalHandler {
 	protected boolean isNamespaceDeclaration(QName qName) {
 		String prefix = qName.getPrefix();
 		String localPart = qName.getLocalPart();
-		return (XMLConstants.XMLNS_ATTRIBUTE.equals(localPart) && prefix.length() == 0) ||
-				(XMLConstants.XMLNS_ATTRIBUTE.equals(prefix) && localPart.length() != 0);
+		return (XMLConstants.XMLNS_ATTRIBUTE.equals(localPart) && prefix.isEmpty()) ||
+				(XMLConstants.XMLNS_ATTRIBUTE.equals(prefix) && !localPart.isEmpty());
 	}
 
 

spring-expression/src/main/java/org/springframework/expression/common/TemplateAwareExpressionParser.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -40,31 +40,28 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 	 * Default ParserContext instance for non-template expressions.
 	 */
 	private static final ParserContext NON_TEMPLATE_PARSER_CONTEXT = new ParserContext() {
-
 		@Override
 		public String getExpressionPrefix() {
 			return null;
 		}
-
 		@Override
 		public String getExpressionSuffix() {
 			return null;
 		}
-
 		@Override
 		public boolean isTemplate() {
 			return false;
 		}
 	};
 
+
 	@Override
 	public Expression parseExpression(String expressionString) throws ParseException {
 		return parseExpression(expressionString, NON_TEMPLATE_PARSER_CONTEXT);
 	}
 
 	@Override
-	public Expression parseExpression(String expressionString, ParserContext context)
-			throws ParseException {
+	public Expression parseExpression(String expressionString, ParserContext context) throws ParseException {
 		if (context == null) {
 			context = NON_TEMPLATE_PARSER_CONTEXT;
 		}
@@ -77,11 +74,12 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 		}
 	}
 
-	private Expression parseTemplate(String expressionString, ParserContext context)
-			throws ParseException {
-		if (expressionString.length() == 0) {
+
+	private Expression parseTemplate(String expressionString, ParserContext context) throws ParseException {
+		if (expressionString.isEmpty()) {
 			return new LiteralExpression("");
 		}
+
 		Expression[] expressions = parseExpressions(expressionString, context);
 		if (expressions.length == 1) {
 			return expressions[0];
@@ -109,8 +107,7 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 	 * @return the parsed expressions
 	 * @throws ParseException when the expressions cannot be parsed
 	 */
-	private Expression[] parseExpressions(String expressionString, ParserContext context)
-			throws ParseException {
+	private Expression[] parseExpressions(String expressionString, ParserContext context) throws ParseException {
 		List<Expression> expressions = new LinkedList<Expression>();
 		String prefix = context.getExpressionPrefix();
 		String suffix = context.getExpressionSuffix();
@@ -120,35 +117,29 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 			if (prefixIndex >= startIdx) {
 				// an inner expression was found - this is a composite
 				if (prefixIndex > startIdx) {
-					expressions.add(createLiteralExpression(context,
-							expressionString.substring(startIdx, prefixIndex)));
+					expressions.add(new LiteralExpression(expressionString.substring(startIdx, prefixIndex)));
 				}
 				int afterPrefixIndex = prefixIndex + prefix.length();
-				int suffixIndex = skipToCorrectEndSuffix(prefix, suffix,
-						expressionString, afterPrefixIndex);
-
+				int suffixIndex = skipToCorrectEndSuffix(suffix, expressionString, afterPrefixIndex);
 				if (suffixIndex == -1) {
 					throw new ParseException(expressionString, prefixIndex,
-							"No ending suffix '" + suffix
-									+ "' for expression starting at character "
-									+ prefixIndex + ": "
-									+ expressionString.substring(prefixIndex));
+							"No ending suffix '" + suffix + "' for expression starting at character " +
+							prefixIndex + ": " + expressionString.substring(prefixIndex));
 				}
 
 				if (suffixIndex == afterPrefixIndex) {
 					throw new ParseException(expressionString, prefixIndex,
-							"No expression defined within delimiter '" + prefix + suffix
-									+ "' at character " + prefixIndex);
+							"No expression defined within delimiter '" + prefix + suffix +
+							"' at character " + prefixIndex);
 				}
 
-				String expr = expressionString.substring(prefixIndex + prefix.length(),
-						suffixIndex);
+				String expr = expressionString.substring(prefixIndex + prefix.length(), suffixIndex);
 				expr = expr.trim();
 
-				if (expr.length() == 0) {
+				if (expr.isEmpty()) {
 					throw new ParseException(expressionString, prefixIndex,
-							"No expression defined within delimiter '" + prefix + suffix
-									+ "' at character " + prefixIndex);
+							"No expression defined within delimiter '" + prefix + suffix +
+							"' at character " + prefixIndex);
 				}
 
 				expressions.add(doParseExpression(expr, context));
@@ -156,18 +147,13 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 			}
 			else {
 				// no more ${expressions} found in string, add rest as static text
-				expressions.add(createLiteralExpression(context,
-						expressionString.substring(startIdx)));
+				expressions.add(new LiteralExpression(expressionString.substring(startIdx)));
 				startIdx = expressionString.length();
 			}
 		}
 		return expressions.toArray(new Expression[expressions.size()]);
 	}
 
-	private Expression createLiteralExpression(ParserContext context, String text) {
-		return new LiteralExpression(text);
-	}
-
 	/**
 	 * Return true if the specified suffix can be found at the supplied position in the
 	 * supplied expression string.
@@ -192,15 +178,15 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 	/**
 	 * Copes with nesting, for example '${...${...}}' where the correct end for the first
 	 * ${ is the final }.
-	 * @param prefix the prefix
 	 * @param suffix the suffix
 	 * @param expressionString the expression string
 	 * @param afterPrefixIndex the most recently found prefix location for which the
-	 *        matching end suffix is being sought
+	 * matching end suffix is being sought
 	 * @return the position of the correct matching nextSuffix or -1 if none can be found
 	 */
-	private int skipToCorrectEndSuffix(String prefix, String suffix,
-			String expressionString, int afterPrefixIndex) throws ParseException {
+	private int skipToCorrectEndSuffix(String suffix, String expressionString, int afterPrefixIndex)
+			throws ParseException {
+
 		// Chew on the expression text - relying on the rules:
 		// brackets must be in pairs: () [] {}
 		// string literals are "..." or '...' and these may contain unmatched brackets
@@ -226,16 +212,15 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 				case ']':
 				case ')':
 					if (stack.isEmpty()) {
-						throw new ParseException(expressionString, pos, "Found closing '"
-								+ ch + "' at position " + pos + " without an opening '"
-								+ Bracket.theOpenBracketFor(ch) + "'");
+						throw new ParseException(expressionString, pos, "Found closing '" + ch +
+								"' at position " + pos + " without an opening '" +
+								Bracket.theOpenBracketFor(ch) + "'");
 					}
 					Bracket p = stack.pop();
 					if (!p.compatibleWithCloseBracket(ch)) {
-						throw new ParseException(expressionString, pos, "Found closing '"
-								+ ch + "' at position " + pos
-								+ " but most recent opening is '" + p.bracket
-								+ "' at position " + p.pos);
+						throw new ParseException(expressionString, pos, "Found closing '" + ch +
+								"' at position " + pos + " but most recent opening is '" + p.bracket +
+								"' at position " + p.pos);
 					}
 					break;
 				case '\'':
@@ -244,8 +229,7 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 					int endLiteral = expressionString.indexOf(ch, pos + 1);
 					if (endLiteral == -1) {
 						throw new ParseException(expressionString, pos,
-								"Found non terminating string literal starting at position "
-										+ pos);
+								"Found non terminating string literal starting at position " + pos);
 					}
 					pos = endLiteral;
 					break;
@@ -254,9 +238,8 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 		}
 		if (!stack.isEmpty()) {
 			Bracket p = stack.pop();
-			throw new ParseException(expressionString, p.pos, "Missing closing '"
-					+ Bracket.theCloseBracketFor(p.bracket) + "' for '" + p.bracket
-					+ "' at position " + p.pos);
+			throw new ParseException(expressionString, p.pos, "Missing closing '" +
+					Bracket.theCloseBracketFor(p.bracket) + "' for '" + p.bracket + "' at position " + p.pos);
 		}
 		if (!isSuffixHere(expressionString, pos, suffix)) {
 			return -1;
@@ -265,6 +248,17 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 	}
 
 
+	/**
+	 * Actually parse the expression string and return an Expression object.
+	 * @param expressionString the raw expression string to parse
+	 * @param context a context for influencing this expression parsing routine (optional)
+	 * @return an evaluator for the parsed expression
+	 * @throws ParseException an exception occurred during parsing
+	 */
+	protected abstract Expression doParseExpression(String expressionString, ParserContext context)
+			throws ParseException;
+
+
 	/**
 	 * This captures a type of bracket and the position in which it occurs in the
 	 * expression. The positional information is used if an error has to be reported
@@ -313,14 +307,4 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
 		}
 	}
 
-	/**
-	 * Actually parse the expression string and return an Expression object.
-	 * @param expressionString the raw expression string to parse
-	 * @param context a context for influencing this expression parsing routine (optional)
-	 * @return an evaluator for the parsed expression
-	 * @throws ParseException an exception occurred during parsing
-	 */
-	protected abstract Expression doParseExpression(String expressionString,
-			ParserContext context) throws ParseException;
-
 }

spring-messaging/src/main/java/org/springframework/messaging/handler/annotation/support/AbstractNamedValueMethodArgumentResolver.java

@@ -143,7 +143,7 @@ public abstract class AbstractNamedValueMethodArgumentResolver implements Handle
 	 */
 	private NamedValueInfo updateNamedValueInfo(MethodParameter parameter, NamedValueInfo info) {
 		String name = info.name;
-		if (info.name.length() == 0) {
+		if (info.name.isEmpty()) {
 			name = parameter.getParameterName();
 			if (name == null) {
 				throw new IllegalArgumentException("Name for argument type [" + parameter.getParameterType().getName() +

spring-web/src/main/java/org/springframework/web/method/annotation/AbstractNamedValueMethodArgumentResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -161,7 +161,7 @@ public abstract class AbstractNamedValueMethodArgumentResolver implements Handle
 	 */
 	private NamedValueInfo updateNamedValueInfo(MethodParameter parameter, NamedValueInfo info) {
 		String name = info.name;
-		if (info.name.length() == 0) {
+		if (info.name.isEmpty()) {
 			name = parameter.getParameterName();
 			if (name == null) {
 				throw new IllegalArgumentException(

spring-web/src/test/java/org/springframework/web/multipart/commons/CommonsMultipartResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -116,7 +116,7 @@ public class CommonsMultipartResolverTests {
 	}
 
 	private void doTestParameters(MultipartHttpServletRequest request) {
-		Set<String> parameterNames = new HashSet<String>();
+		Set<String> parameterNames = new HashSet<>();
 		Enumeration<String> parameterEnum = request.getParameterNames();
 		while (parameterEnum.hasMoreElements()) {
 			parameterNames.add(parameterEnum.nextElement());
@@ -137,8 +137,8 @@ public class CommonsMultipartResolverTests {
 		assertEquals("value4", request.getParameter("field4"));
 		assertEquals("getValue", request.getParameter("getField"));
 
-		List<String> parameterMapKeys = new ArrayList<String>();
-		List<Object> parameterMapValues = new ArrayList<Object>();
+		List<String> parameterMapKeys = new ArrayList<>();
+		List<Object> parameterMapValues = new ArrayList<>();
 		for (Object o : request.getParameterMap().keySet()) {
 			String key = (String) o;
 			parameterMapKeys.add(key);
@@ -165,7 +165,7 @@ public class CommonsMultipartResolverTests {
 	}
 
 	private void doTestFiles(MultipartHttpServletRequest request) throws IOException {
-		Set<String> fileNames = new HashSet<String>();
+		Set<String> fileNames = new HashSet<>();
 		Iterator<String> fileIter = request.getFileNames();
 		while (fileIter.hasNext()) {
 			fileNames.add(fileIter.next());
@@ -258,13 +258,13 @@ public class CommonsMultipartResolverTests {
 		binder.setBindEmptyMultipartFiles(false);
 		String firstBound = mtb2.getField2();
 		binder.bind(request);
-		assertTrue(mtb2.getField2().length() > 0);
+		assertFalse(mtb2.getField2().isEmpty());
 		assertEquals(firstBound, mtb2.getField2());
 
 		request = resolver.resolveMultipart(originalRequest);
 		binder.setBindEmptyMultipartFiles(true);
 		binder.bind(request);
-		assertTrue(mtb2.getField2().length() == 0);
+		assertTrue(mtb2.getField2().isEmpty());
 	}
 
 	@Test
@@ -284,7 +284,7 @@ public class CommonsMultipartResolverTests {
 		final MultipartFilter filter = new MultipartFilter();
 		filter.init(filterConfig);
 
-		final List<MultipartFile> files = new ArrayList<MultipartFile>();
+		final List<MultipartFile> files = new ArrayList<>();
 		final FilterChain filterChain = new FilterChain() {
 			@Override
 			public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse) {
@@ -322,7 +322,7 @@ public class CommonsMultipartResolverTests {
 		MockFilterConfig filterConfig = new MockFilterConfig(wac.getServletContext(), "filter");
 		filterConfig.addInitParameter("multipartResolverBeanName", "myMultipartResolver");
 
-		final List<MultipartFile> files = new ArrayList<MultipartFile>();
+		final List<MultipartFile> files = new ArrayList<>();
 		FilterChain filterChain = new FilterChain() {
 			@Override
 			public void doFilter(ServletRequest originalRequest, ServletResponse response) {
@@ -377,7 +377,7 @@ public class CommonsMultipartResolverTests {
 					if (request instanceof MultipartHttpServletRequest) {
 						throw new IllegalStateException("Already a multipart request");
 					}
-					List<FileItem> fileItems = new ArrayList<FileItem>();
+					List<FileItem> fileItems = new ArrayList<>();
 					MockFileItem fileItem1 = new MockFileItem(
 						"field1", "type1", empty ? "" : "field1.txt", empty ? "" : "text1");
 					MockFileItem fileItem1x = new MockFileItem(

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestPartMethodArgumentResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -159,7 +159,7 @@ public class RequestPartMethodArgumentResolver extends AbstractMessageConverterM
 
 	private String getPartName(MethodParameter methodParam, RequestPart requestPart) {
 		String partName = (requestPart != null ? requestPart.name() : "");
-		if (partName.length() == 0) {
+		if (partName.isEmpty()) {
 			partName = methodParam.getParameterName();
 			if (partName == null) {
 				throw new IllegalArgumentException("Request part name for argument type [" +

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/SseEmitter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -25,6 +25,7 @@ import java.util.Set;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.server.ServerHttpResponse;
+import org.springframework.util.StringUtils;
 
 /**
  * A specialization of {@link ResponseBodyEmitter} for sending
@@ -234,7 +235,7 @@ public class SseEmitter extends ResponseBodyEmitter {
 
 		@Override
 		public Set<DataWithMediaType> build() {
-			if ((this.sb == null || this.sb.length() == 0) && this.dataToSend.isEmpty()) {
+			if (!StringUtils.hasLength(this.sb) && this.dataToSend.isEmpty()) {
 				return Collections.<DataWithMediaType>emptySet();
 			}
 			append("\n");