Switching StringBuffer to StringBuilder throughout the codebase (APIs permitting).

core/src/main/java/org/springframework/security/access/intercept/RunAsUserToken.java

@@ -73,7 +73,7 @@ public class RunAsUserToken extends AbstractAuthenticationToken {
     }
 
     public String toString() {
-        StringBuffer sb = new StringBuffer(super.toString());
+        StringBuilder sb = new StringBuilder(super.toString());
         sb.append("; Original Class: ").append(this.originalAuthentication.getName());
 
         return sb.toString();

core/src/main/java/org/springframework/security/authentication/AuthenticationDetails.java

@@ -59,7 +59,7 @@ public class AuthenticationDetails implements Serializable {
    }
 
    public String toString() {
-       StringBuffer sb = new StringBuffer();
+       StringBuilder sb = new StringBuilder();
        sb.append(super.toString() + ": ");
        sb.append("Context: " + this.getContext());
 

core/src/main/java/org/springframework/security/core/authority/GrantedAuthoritiesContainerImpl.java

@@ -19,7 +19,7 @@ public class GrantedAuthoritiesContainerImpl implements MutableGrantedAuthoritie
     }
 
     public String toString() {
-        StringBuffer sb = new StringBuffer();
+        StringBuilder sb = new StringBuilder();
         sb.append("Authorities: ").append(authorities);
         return sb.toString();
     }

core/src/main/java/org/springframework/security/core/context/SecurityContextImpl.java

@@ -66,7 +66,7 @@ public class SecurityContextImpl implements SecurityContext {
     }
 
     public String toString() {
-        StringBuffer sb = new StringBuffer();
+        StringBuilder sb = new StringBuilder();
         sb.append(super.toString());
 
         if (this.authentication == null) {

core/src/main/java/org/springframework/security/core/token/KeyBasedPersistenceTokenService.java

@@ -91,7 +91,7 @@ public class KeyBasedPersistenceTokenService implements TokenService, Initializi
         String pseudoRandomNumber = tokens[1];
 
         // Permit extendedInfo to itself contain ":" characters
-        StringBuffer extendedInfo = new StringBuffer();
+        StringBuilder extendedInfo = new StringBuilder();
         for (int i = 2; i < tokens.length-1; i++) {
             if (i > 2) {
                 extendedInfo.append(":");