diff --git a/spring-boot-project/spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/web/servlet/WebDriverContextCustomizerFactory.java b/spring-boot-project/spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/web/servlet/WebDriverContextCustomizerFactory.java
index de8c55c9fc..39e1c04fca 100644
--- a/spring-boot-project/spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/web/servlet/WebDriverContextCustomizerFactory.java
+++ b/spring-boot-project/spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/web/servlet/WebDriverContextCustomizerFactory.java
@@ -59,7 +59,7 @@ class WebDriverContextCustomizerFactory implements ContextCustomizerFactory {
 			if (obj == this) {
 				return true;
 			}
-			if (obj == null || !obj.getClass().equals(getClass())) {
+			if (obj == null || obj.getClass() != getClass()) {
 				return false;
 			}
 			return true;
diff --git a/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactive/WebTestClientContextCustomizer.java b/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactive/WebTestClientContextCustomizer.java
index 68dcc2fe74..3279677dea 100644
--- a/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactive/WebTestClientContextCustomizer.java
+++ b/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/reactive/WebTestClientContextCustomizer.java
@@ -74,7 +74,7 @@ class WebTestClientContextCustomizer implements ContextCustomizer {
 
 	@Override
 	public boolean equals(Object obj) {
-		return (obj != null && obj.getClass().equals(getClass()));
+		return (obj != null && obj.getClass() == getClass());
 	}
 
 	/**
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/AsciiBytes.java b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/AsciiBytes.java
index 75d47cc57e..d828c2aacc 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/AsciiBytes.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/AsciiBytes.java
@@ -211,7 +211,7 @@ final class AsciiBytes {
 		if (this == obj) {
 			return true;
 		}
-		if (obj.getClass().equals(AsciiBytes.class)) {
+		if (obj.getClass() == AsciiBytes.class) {
 			AsciiBytes other = (AsciiBytes) obj;
 			if (this.length == other.length) {
 				for (int i = 0; i < this.length; i++) {
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertyName.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertyName.java
index 7b8ac56812..c7a1cada67 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertyName.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertyName.java
@@ -355,7 +355,7 @@ public final class ConfigurationPropertyName
 		if (obj == this) {
 			return true;
 		}
-		if (obj == null || !obj.getClass().equals(getClass())) {
+		if (obj == null || obj.getClass() != getClass()) {
 			return false;
 		}
 		ConfigurationPropertyName other = (ConfigurationPropertyName) obj;
@@ -410,8 +410,11 @@ public final class ConfigurationPropertyName
 
 	private static boolean isIndexed(CharSequence element) {
 		int length = element.length();
-		return length > 2 && element.charAt(0) == '['
-				&& element.charAt(length - 1) == ']';
+		return charAt(element, 0) == '[' && charAt(element, length - 1) == ']';
+	}
+
+	private static char charAt(CharSequence element, int index) {
+		return (index < element.length() ? element.charAt(index) : 0);
 	}
 
 	/**
@@ -496,7 +499,7 @@ public final class ConfigurationPropertyName
 		if (name.length() == 0) {
 			return EMPTY;
 		}
-		List<CharSequence> elements = new ArrayList<>(10);
+		List<CharSequence> elements = new ArrayList<>();
 		process(name, separator, (elementValue, start, end, indexed) -> {
 			elementValue = elementValueProcessor.apply(elementValue);
 			if (!isIndexed(elementValue)) {
@@ -656,10 +659,16 @@ public final class ConfigurationPropertyName
 		}
 
 		public static boolean isValidElement(CharSequence elementValue) {
-			return getInvalidChars(elementValue).isEmpty();
+			for (int i = 0; i < elementValue.length(); i++) {
+				char ch = elementValue.charAt(i);
+				if (!isValidChar(ch, i)) {
+					return false;
+				}
+			}
+			return true;
 		}
 
-		private static List<Character> getInvalidChars(CharSequence elementValue) {
+		public static List<Character> getInvalidChars(CharSequence elementValue) {
 			List<Character> chars = new ArrayList<>();
 			for (int i = 0; i < elementValue.length(); i++) {
 				char ch = elementValue.charAt(i);
@@ -671,12 +680,15 @@ public final class ConfigurationPropertyName
 		}
 
 		public static boolean isValidChar(char ch, int index) {
-			boolean isAlpha = ch >= 'a' && ch <= 'z';
-			boolean isNumeric = ch >= '0' && ch <= '9';
-			if (index == 0) {
-				return isAlpha;
-			}
-			return isAlpha || isNumeric || ch == '-';
+			return isAlpha(ch) || (index != 0 && (isNumeric(ch) || ch == '-'));
+		}
+
+		private static boolean isAlpha(char ch) {
+			return ch >= 'a' && ch <= 'z';
+		}
+
+		private static boolean isNumeric(char ch) {
+			return ch >= '0' && ch <= '9';
 		}
 
 	}