8274898: Cleanup usages of StringBuffer in jdk tools modules

Reviewed-by: sspitsyn, lmesnik

Author: turbanoff

src/jdk.jartool/share/classes/sun/security/tools/jarsigner/Main.java

@@ -834,9 +834,9 @@ void verifyJar(String jarName)
                     }
 
                     // Only used when -verbose provided
-                    StringBuffer sb = null;
+                    StringBuilder sb = null;
                     if (verbose != null) {
-                        sb = new StringBuffer();
+                        sb = new StringBuilder();
                         boolean inManifest =
                             ((man.getAttributes(name) != null) ||
                              (man.getAttributes("./"+name) != null) ||

src/jdk.jpackage/share/classes/jdk/jpackage/internal/Log.java

@@ -108,21 +108,21 @@ public void verbose(String msg) {
         public void verbose(List<String> strings,
                 List<String> output, int returnCode, long pid) {
             if (verbose) {
-                StringBuffer sb = new StringBuffer();
+                StringBuilder sb = new StringBuilder();
                 sb.append("Command [PID: ");
                 sb.append(pid);
                 sb.append("]:\n   ");
 
                 for (String s : strings) {
                     sb.append(" " + s);
                 }
-                verbose(new String(sb));
+                verbose(sb.toString());
                 if (output != null && !output.isEmpty()) {
-                    sb = new StringBuffer("Output:");
+                    sb = new StringBuilder("Output:");
                     for (String s : output) {
                         sb.append("\n    " + s);
                     }
-                    verbose(new String(sb));
+                    verbose(sb.toString());
                 }
                 verbose("Returned: " + returnCode + "\n");
             }

src/jdk.jshell/share/classes/jdk/internal/jshell/tool/Feedback.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -372,7 +372,7 @@ String format(String field, Selector selector) {
                 return "";
             }
             Matcher m = FIELD_PATTERN.matcher(format);
-            StringBuffer sb = new StringBuffer(format.length());
+            StringBuilder sb = new StringBuilder(format.length());
             while (m.find()) {
                 String fieldName = m.group(1);
                 String sub = format(fieldName, selector);