Use isEmpty() where possible

See gh-20370

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/TotalProgressBar.java

@@ -63,7 +63,7 @@ public class TotalProgressBar implements Consumer<TotalProgressEvent> {
 	public TotalProgressBar(String prefix, char progressChar, boolean bookend, PrintStream out) {
 		this.progressChar = progressChar;
 		this.bookend = bookend;
-		if (prefix != null && prefix.length() > 0) {
+		if (prefix != null && !prefix.isEmpty()) {
 			out.print(prefix);
 			out.print(" ");
 		}

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/TypeUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -154,7 +154,7 @@ class TypeUtils {
 		if (((TypeElement) this.types.asElement(type)).getQualifiedName().contentEquals(Collection.class.getName())) {
 			DeclaredType declaredType = (DeclaredType) type;
 			// raw type, just "Collection"
-			if (declaredType.getTypeArguments().size() == 0) {
+			if (declaredType.getTypeArguments().isEmpty()) {
 				return this.types.getDeclaredType(this.env.getElementUtils().getTypeElement(Object.class.getName()));
 			}
 			// return type argument to Collection<...>

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/main/java/org/springframework/boot/jarmode/layertools/Context.java

@@ -62,7 +62,7 @@ class Context {
 			return null;
 		}
 		String relativePath = sourcePath.substring(workingPath.length() + 1);
-		return (relativePath.length() > 0) ? relativePath : null;
+		return !relativePath.isEmpty() ? relativePath : null;
 	}
 
 	/**