HADOOP-19134. Use StringBuilder instead of StringBuffer. (#6692). Contributed by PJ Fanning

Author: pjfanning

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/crypto/key/KeyShell.java

@@ -169,7 +169,7 @@ protected int init(String[] args) throws IOException {
 
   @Override
   public String getCommandUsage() {
-    StringBuffer sbuf = new StringBuffer(USAGE_PREFIX + COMMANDS);
+    StringBuilder sbuf = new StringBuilder(USAGE_PREFIX + COMMANDS);
     String banner = StringUtils.repeat("=", 66);
     sbuf.append(banner + "\n");
     sbuf.append(CreateCommand.USAGE + ":\n\n" + CreateCommand.DESC + "\n");

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/DF.java

@@ -163,7 +163,7 @@ protected void parseExecResult(BufferedReader lines) throws IOException {
   @VisibleForTesting
   protected void parseOutput() throws IOException {
     if (output.size() < 2) {
-      StringBuffer sb = new StringBuffer("Fewer lines of output than expected");
+      StringBuilder sb = new StringBuilder("Fewer lines of output than expected");
       if (output.size() > 0) {
         sb.append(": " + output.get(0));
       }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileUtil.java

@@ -1052,7 +1052,7 @@ private static void unTarUsingTar(InputStream inputStream, File untarDir,
 
   private static void unTarUsingTar(File inFile, File untarDir,
       boolean gzipped) throws IOException {
-    StringBuffer untarCommand = new StringBuffer();
+    StringBuilder untarCommand = new StringBuilder();
     // not using canonical path here; this postpones relative path
     // resolution until bash is executed.
     final String source = "'" + FileUtil.makeSecureShellPath(inFile) + "'";

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/oncrpc/RpcDeniedReply.java

@@ -58,7 +58,7 @@ public RejectState getRejectState() {
 
   @Override
   public String toString() {
-    return new StringBuffer().append("xid:").append(xid)
+    return new StringBuilder().append("xid:").append(xid)
         .append(",messageType:").append(messageType).append("verifier_flavor:")
         .append(verifier.getFlavor()).append("rejectState:")
         .append(rejectState).toString();

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/ProviderUtils.java

@@ -148,7 +148,7 @@ public static Configuration excludeIncompatibleCredentialProviders(
     if (providerPath == null) {
       return config;
     }
-    StringBuffer newProviderPath = new StringBuffer();
+    StringBuilder newProviderPath = new StringBuilder();
     String[] providers = providerPath.split(",");
     Path path = null;
     for (String provider: providers) {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/alias/CredentialShell.java

@@ -127,7 +127,7 @@ protected int init(String[] args) throws IOException {
 
   @Override
   public String getCommandUsage() {
-    StringBuffer sbuf = new StringBuffer(USAGE_PREFIX + COMMANDS);
+    StringBuilder sbuf = new StringBuilder(USAGE_PREFIX + COMMANDS);
     String banner = StringUtils.repeat("=", 66);
     sbuf.append(banner + "\n")
         .append(CreateCommand.USAGE + ":\n\n" + CreateCommand.DESC + "\n")

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/ssl/SSLHostnameVerifier.java

@@ -370,7 +370,7 @@ public void check(final String[] hosts, final String[] cns,
                     strictWithSubDomains);
             }
             // Build up lists of allowed hosts For logging/debugging purposes.
-            StringBuffer buf = new StringBuffer(32);
+            StringBuilder buf = new StringBuilder(32);
             buf.append('<');
             for (int i = 0; i < hosts.length; i++) {
                 String h = hosts[i];
@@ -408,15 +408,15 @@ public void check(final String[] hosts, final String[] cns,
                 throw new SSLException(msg);
             }
 
-            // StringBuffer for building the error message.
-            buf = new StringBuffer();
+            // StringBuilder for building the error message.
+            buf = new StringBuilder();
 
             boolean match = false;
             out:
             for (Iterator<String> it = names.iterator(); it.hasNext();) {
                 // Don't trim the CN, though!
                 final String cn = StringUtils.toLowerCase(it.next());
-                // Store CN in StringBuffer in case we need to report an error.
+                // Store CN in StringBuilder in case we need to report an error.
             buf.append(" <")
             .append(cn)
             .append('>');

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/Shell.java

@@ -1014,7 +1014,7 @@ private void runCommand() throws IOException {
     BufferedReader inReader =
             new BufferedReader(new InputStreamReader(process.getInputStream(),
                 StandardCharsets.UTF_8));
-    final StringBuffer errMsg = new StringBuffer();
+    final StringBuilder errMsg = new StringBuilder();
 
     // read error and input streams as this would free up the buffers
     // free the error stream buffer
@@ -1208,7 +1208,7 @@ public static class ShellCommandExecutor extends Shell
       implements CommandExecutor {
 
     private String[] command;
-    private StringBuffer output;
+    private StringBuilder output;
 
 
     public ShellCommandExecutor(String[] execString) {
@@ -1289,7 +1289,7 @@ public String[] getExecString() {
 
     @Override
     protected void parseExecResult(BufferedReader lines) throws IOException {
-      output = new StringBuffer();
+      output = new StringBuilder();
       char[] buf = new char[512];
       int nRead;
       while ( (nRead = lines.read(buf, 0, buf.length)) > 0 ) {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java

@@ -1334,7 +1334,7 @@ public static String wrap(String str, int wrapLength, String newLineStr,
 
       int inputLineLength = str.length();
       int offset = 0;
-      StringBuffer wrappedLine = new StringBuffer(inputLineLength + 32);
+      StringBuilder wrappedLine = new StringBuilder(inputLineLength + 32);
 
       while(inputLineLength - offset > wrapLength) {
         if(str.charAt(offset) == 32) {

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/shell/TestCount.java

@@ -580,7 +580,7 @@ public MockQuotaUsage() {
     public String toString(boolean hOption,
         boolean tOption, List<StorageType> types) {
       if (tOption) {
-        StringBuffer result = new StringBuffer();
+        StringBuilder result = new StringBuilder();
         result.append(hOption ? HUMAN : BYTES);
 
         for (StorageType type : types) {