Sort methods to align with PropertySource declaration order

See gh-34861

Author: sbrannen

spring-context/src/main/java/org/springframework/context/support/PropertySourcesPlaceholderConfigurer.java

@@ -233,25 +233,25 @@ private static class ConfigurableEnvironmentPropertySource extends PropertySourc
 
 
 		@Override
-		@Nullable
-		public Object getProperty(String name) {
+		public boolean containsProperty(String name) {
 			for (PropertySource<?> propertySource : super.source.getPropertySources()) {
-				Object candidate = propertySource.getProperty(name);
-				if (candidate != null) {
-					return candidate;
+				if (propertySource.containsProperty(name)) {
+					return true;
 				}
 			}
-			return null;
+			return false;
 		}
 
 		@Override
-		public boolean containsProperty(String name) {
+		@Nullable
+		public Object getProperty(String name) {
 			for (PropertySource<?> propertySource : super.source.getPropertySources()) {
-				if (propertySource.containsProperty(name)) {
-					return true;
+				Object candidate = propertySource.getProperty(name);
+				if (candidate != null) {
+					return candidate;
 				}
 			}
-			return false;
+			return null;
 		}
 
 		@Override
@@ -274,14 +274,14 @@ private static class FallbackEnvironmentPropertySource extends PropertySource<En
 
 
 		@Override
-		@Nullable
-		public Object getProperty(String name) {
-			return super.source.getProperty(name);
+		public boolean containsProperty(String name) {
+			return super.source.containsProperty(name);
 		}
 
 		@Override
-		public boolean containsProperty(String name) {
-			return super.source.containsProperty(name);
+		@Nullable
+		public Object getProperty(String name) {
+			return super.source.getProperty(name);
 		}
 
 		@Override