Polish "Use java.util.HexFormat where appropriate"

See gh-31477

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/system/ApplicationTemp.java

@@ -27,6 +27,7 @@ import java.nio.file.attribute.PosixFilePermission;
 import java.nio.file.attribute.PosixFilePermissions;
 import java.security.MessageDigest;
 import java.util.EnumSet;
+import java.util.HexFormat;
 
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
@@ -41,8 +42,6 @@ import org.springframework.util.StringUtils;
  */
 public class ApplicationTemp {
 
-	private static final char[] HEX_CHARS = "0123456789ABCDEF".toCharArray();
-
 	private static final FileAttribute<?>[] NO_FILE_ATTRIBUTES = {};
 
 	private static final EnumSet<PosixFilePermission> DIRECTORY_PERMISSIONS = EnumSet.of(PosixFilePermission.OWNER_READ,
@@ -92,7 +91,7 @@ public class ApplicationTemp {
 	private Path getPath() {
 		if (this.path == null) {
 			synchronized (this) {
-				String hash = toHexString(generateHash(this.sourceClass));
+				String hash = HexFormat.of().withUpperCase().formatHex(generateHash(this.sourceClass));
 				this.path = createDirectory(getTempDirectory().resolve(hash));
 			}
 		}
@@ -160,14 +159,4 @@ public class ApplicationTemp {
 		return source.toString().getBytes();
 	}
 
-	private String toHexString(byte[] bytes) {
-		char[] hex = new char[bytes.length * 2];
-		for (int i = 0; i < bytes.length; i++) {
-			int b = bytes[i] & 0xFF;
-			hex[i * 2] = HEX_CHARS[b >>> 4];
-			hex[i * 2 + 1] = HEX_CHARS[b & 0x0F];
-		}
-		return new String(hex);
-	}
-
 }