diff --git a/src/main/java/org/mindrot/BCrypt.java b/src/main/java/org/mindrot/BCrypt.java
index 188193f..2427771 100644
--- a/src/main/java/org/mindrot/BCrypt.java
+++ b/src/main/java/org/mindrot/BCrypt.java
@@ -388,7 +388,7 @@ public class BCrypt {
 	private static String encode_base64(byte d[], int len)
 		throws IllegalArgumentException {
 		int off = 0;
-		StringBuffer rs = new StringBuffer();
+		StringBuilder rs = new StringBuilder();
 		int c1, c2;
 
 		if (len <= 0 || len > d.length)
@@ -441,7 +441,7 @@ private static byte char64(char x) {
 	 */
 	private static byte[] decode_base64(String s, int maxolen)
 		throws IllegalArgumentException {
-		StringBuffer rs = new StringBuffer();
+		StringBuilder rs = new StringBuilder();
 		int off = 0, slen = s.length(), olen = 0;
 		byte ret[];
 		byte c1, c2, c3, c4, o;
@@ -654,7 +654,7 @@ public static String hashpw(String password, String salt) {
 		byte passwordb[], saltb[], hashed[];
 		char minor = (char)0;
 		int rounds, off = 0;
-		StringBuffer rs = new StringBuffer();
+		StringBuilder rs = new StringBuilder();
 
 		if (salt.charAt(0) != '$' || salt.charAt(1) != '2')
 			throw new IllegalArgumentException ("Invalid salt version");
@@ -712,7 +712,7 @@ public static String hashpw(String password, String salt) {
 	 * @return	an encoded salt value
 	 */
 	public static String gensalt(int log_rounds, SecureRandom random) {
-		StringBuffer rs = new StringBuffer();
+		StringBuilder rs = new StringBuilder();
 		byte rnd[] = new byte[BCRYPT_SALT_LEN];
 
 		random.nextBytes(rnd);