Use String#isEmpty where possible (#7690)

core/src/main/java/hudson/EnvVars.java

@@ -144,7 +144,7 @@ public class EnvVars extends TreeMap<String, String> {
      * Handles {@code PATH+XYZ} notation.
      */
     public void override(String key, String value) {
-        if (value == null || value.length() == 0) {
+        if (value == null || value.isEmpty()) {
             remove(key);
             return;
         }

core/src/main/java/hudson/Functions.java

@@ -1655,7 +1655,7 @@ public class Functions {
      * Converts "abc" to "Abc".
      */
     public static String capitalize(String s) {
-        if (s == null || s.length() == 0) return s;
+        if (s == null || s.isEmpty()) return s;
         return Character.toUpperCase(s.charAt(0)) + s.substring(1);
     }
 
@@ -1867,7 +1867,7 @@ public class Functions {
     public static String joinPath(String... components) {
         StringBuilder buf = new StringBuilder();
         for (String s : components) {
-            if (s.length() == 0)  continue;
+            if (s.isEmpty())  continue;
 
             if (buf.length() > 0) {
                 if (buf.charAt(buf.length() - 1) != '/')

core/src/main/java/hudson/PluginManager.java

@@ -662,7 +662,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
 
         for (String pluginPath : plugins) {
             String fileName = pluginPath.substring(pluginPath.lastIndexOf('/') + 1);
-            if (fileName.length() == 0) {
+            if (fileName.isEmpty()) {
                 // see http://www.nabble.com/404-Not-Found-error-when-clicking-on-help-td24508544.html
                 // I suspect some containers are returning directory names.
                 continue;

core/src/main/java/hudson/ProxyConfiguration.java

@@ -222,7 +222,7 @@ public final class ProxyConfiguration extends AbstractDescribableImpl<ProxyConfi
 
         List<Pattern> r = new ArrayList<>();
         for (String s : noProxyHost.split("[ \t\n,|]+")) {
-            if (s.length() == 0)  continue;
+            if (s.isEmpty())  continue;
             r.add(Pattern.compile(s.replace(".", "\\.").replace("*", ".*")));
         }
         return r;

core/src/main/java/hudson/Util.java

@@ -1110,7 +1110,7 @@ public class Util {
      */
     @CheckForNull
     public static String fixEmpty(@CheckForNull String s) {
-        if (s == null || s.length() == 0)    return null;
+        if (s == null || s.isEmpty())    return null;
         return s;
     }
 
@@ -1487,7 +1487,7 @@ public class Util {
      */
     @CheckForNull
     public static Number tryParseNumber(@CheckForNull String numberStr, @CheckForNull Number defaultNumber) {
-        if (numberStr == null || numberStr.length() == 0) {
+        if (numberStr == null || numberStr.isEmpty()) {
             return defaultNumber;
         }
         try {

core/src/main/java/hudson/init/TaskMethodFinder.java

@@ -82,7 +82,7 @@ abstract class TaskMethodFinder<T extends Annotation> extends TaskBuilder {
     protected String getDisplayNameOf(Method e, T i) {
         Class<?> c = e.getDeclaringClass();
         String key = displayNameOf(i);
-        if (key.length() == 0)  return c.getSimpleName() + "." + e.getName();
+        if (key.isEmpty())  return c.getSimpleName() + "." + e.getName();
         try {
             ResourceBundleHolder rb = ResourceBundleHolder.get(
                     c.getClassLoader().loadClass(c.getPackage().getName() + ".Messages"));

core/src/main/java/hudson/logging/LogRecorder.java

@@ -312,27 +312,27 @@ public class LogRecorder extends AbstractModelObject implements Saveable {
         public boolean includes(LogRecord r) {
             if (r.getLevel().intValue() < level)
                 return false;   // below the threshold
-            if (name.length() == 0) {
+            if (name.isEmpty()) {
                 return true; // like root logger, includes everything
             }
             String logName = r.getLoggerName();
             if (logName == null || !logName.startsWith(name))
                 return false;   // not within this logger
             String rest = logName.substring(name.length());
-            return rest.startsWith(".") || rest.length() == 0;
+            return rest.startsWith(".") || rest.isEmpty();
         }
 
         @SuppressFBWarnings(value = "NP_BOOLEAN_RETURN_NULL", justification = "converting this to YesNoMaybe would break backward compatibility")
         public Boolean matches(LogRecord r) {
             boolean levelSufficient = r.getLevel().intValue() >= level;
-            if (name.length() == 0) {
+            if (name.isEmpty()) {
                 return levelSufficient; // include if level matches
             }
             String logName = r.getLoggerName();
             if (logName == null || !logName.startsWith(name))
                 return null; // not in the domain of this logger
             String rest = logName.substring(name.length());
-            if (rest.startsWith(".") || rest.length() == 0) {
+            if (rest.startsWith(".") || rest.isEmpty()) {
                 return levelSufficient; // include if level matches
             }
             return null;

core/src/main/java/hudson/model/AbstractBuild.java

@@ -210,7 +210,7 @@ public abstract class AbstractBuild<P extends AbstractProject<P, R>, R extends A
      *      null, for example if the agent that this build run no longer exists.
      */
     public @CheckForNull Node getBuiltOn() {
-        if (builtOn == null || builtOn.equals(""))
+        if (builtOn == null || builtOn.isEmpty())
             return Jenkins.get();
         else
             return Jenkins.get().getNode(builtOn);

core/src/main/java/hudson/model/AbstractItem.java

@@ -479,7 +479,7 @@ public abstract class AbstractItem extends Actionable implements Item, HttpDelet
     @Exported
     public final String getFullName() {
         String n = getParent().getFullName();
-        if (n.length() == 0)   return getName();
+        if (n.isEmpty())   return getName();
         else                return n + '/' + getName();
     }
 
@@ -487,7 +487,7 @@ public abstract class AbstractItem extends Actionable implements Item, HttpDelet
     @Exported
     public final String getFullDisplayName() {
         String n = getParent().getFullDisplayName();
-        if (n.length() == 0)   return getDisplayName();
+        if (n.isEmpty())   return getDisplayName();
         else                return n + " » " + getDisplayName();
     }
 

core/src/main/java/hudson/model/AbstractProject.java

@@ -683,7 +683,7 @@ public abstract class AbstractProject<P extends AbstractProject<P, R>, R extends
      */
     public FormValidation doCheckRetryCount(@QueryParameter String value)throws IOException, ServletException {
         // retry count is optional so this is ok
-        if (value == null || value.trim().equals(""))
+        if (value == null || value.trim().isEmpty())
             return FormValidation.ok();
         if (!value.matches("[0-9]*")) {
             return FormValidation.error("Invalid retry count");

core/src/main/java/hudson/model/AutoCompletionCandidates.java

@@ -149,7 +149,7 @@ public class AutoCompletionCandidates implements HttpResponse {
             }
 
             private String contextualNameOf(Item i) {
-                if (prefix.endsWith("/") || prefix.length() == 0)
+                if (prefix.endsWith("/") || prefix.isEmpty())
                     return prefix + i.getName();
                 else
                     return prefix + '/' + i.getName();

core/src/main/java/hudson/model/Descriptor.java

@@ -440,8 +440,8 @@ public abstract class Descriptor<T extends Describable<T>> implements Saveable,
             QueryParameter qp = p.annotation(QueryParameter.class);
             if (qp != null) {
                 String name = qp.value();
-                if (name.length() == 0) name = p.name();
-                if (name == null || name.length() == 0)
+                if (name.isEmpty()) name = p.name();
+                if (name == null || name.isEmpty())
                     continue;   // unknown parameter name. we'll report the error when the form is submitted.
 
                 RelativePath rp = p.annotation(RelativePath.class);

core/src/main/java/hudson/model/DirectoryBrowserSupport.java

@@ -306,7 +306,7 @@ public final class DirectoryBrowserSupport implements HttpResponse {
                 return;
             }
 
-            if (rest.length() == 0) {
+            if (rest.isEmpty()) {
                 // if the target page to be displayed is a directory and the path doesn't end with '/', redirect
                 StringBuffer reqUrl = req.getRequestURL();
                 if (reqUrl.charAt(reqUrl.length() - 1) != '/') {
@@ -408,7 +408,7 @@ public final class DirectoryBrowserSupport implements HttpResponse {
                 if (!ResourceDomainConfiguration.isResourceRequest(req)) {
                     // if we're serving this from the main domain, set CSP headers
                     String csp = SystemProperties.getString(CSP_PROPERTY_NAME, DEFAULT_CSP_VALUE);
-                    if (!csp.trim().equals("")) {
+                    if (!csp.trim().isEmpty()) {
                         // allow users to prevent sending this header by setting empty system property
                         for (String header : new String[]{"Content-Security-Policy", "X-WebKit-CSP", "X-Content-Security-Policy"}) {
                             rsp.setHeader(header, csp);
@@ -500,7 +500,7 @@ public final class DirectoryBrowserSupport implements HttpResponse {
 
     private String getPath(StaplerRequest req) {
         String path = req.getRestOfPath();
-        if (path.length() == 0)
+        if (path.isEmpty())
             path = "/";
         return path;
     }

core/src/main/java/hudson/model/Items.java

@@ -255,17 +255,17 @@ public class Items {
 
         Stack<String> name = new Stack<>();
         for (int i = 0; i < c.length; i++) {
-            if (i == 0 && c[i].equals("")) continue;
+            if (i == 0 && c[i].isEmpty()) continue;
             name.push(c[i]);
         }
         for (int i = 0; i < p.length; i++) {
-            if (i == 0 && p[i].equals("")) {
+            if (i == 0 && p[i].isEmpty()) {
                 // Absolute path starting with a "/"
                 name.clear();
                 continue;
             }
             if (p[i].equals("..")) {
-                if (name.size() == 0) {
+                if (name.isEmpty()) {
                     throw new IllegalArgumentException(String.format(
                             "Illegal relative path '%s' within context '%s'", path, context.getFullName()
                     ));

core/src/main/java/hudson/model/Slave.java

@@ -201,7 +201,7 @@ public abstract class Slave extends Node implements Serializable {
 
         this.nodeProperties.replaceBy(nodeProperties);
 
-        if (name.equals(""))
+        if (name.isEmpty())
             throw new FormException(Messages.Slave_InvalidConfig_NoName(), null);
 
         if (this.numExecutors <= 0)

core/src/main/java/hudson/model/View.java

@@ -1357,7 +1357,7 @@ public abstract class View extends AbstractModelObject implements AccessControll
         if (owner.getView(name) != null)
             throw new Failure(Messages.Hudson_ViewAlreadyExists(name));
 
-        if (mode == null || mode.length() == 0) {
+        if (mode == null || mode.isEmpty()) {
             if (isXmlSubmission) {
                 View v = createViewFromXML(name, req.getInputStream());
                 owner.getACL().checkCreatePermission(owner, v.getDescriptor());

core/src/main/java/hudson/scheduler/CronTabList.java

@@ -123,7 +123,7 @@ public final class CronTabList {
                 continue;
             }
 
-            if (line.length() == 0 || line.startsWith("#"))
+            if (line.isEmpty() || line.startsWith("#"))
                 continue;   // ignorable line
             try {
                 r.add(new CronTab(line, lineNumber, hash, timezone));

core/src/main/java/hudson/scm/SCM.java

@@ -749,7 +749,7 @@ public abstract class SCM implements Describable<SCM>, ExtensionPoint {
 
     protected final String nullify(String s) {
         if (s == null)     return null;
-        if (s.trim().length() == 0)    return null;
+        if (s.trim().isEmpty())    return null;
         return s;
     }
 

core/src/main/java/hudson/security/HudsonPrivateSecurityRealm.java

@@ -420,7 +420,7 @@ public class HudsonPrivateSecurityRealm extends AbstractPasswordBasedSecurityRea
             si.errors.put("captcha", Messages.HudsonPrivateSecurityRealm_CreateAccount_TextNotMatchWordInImage());
         }
 
-        if (si.username == null || si.username.length() == 0) {
+        if (si.username == null || si.username.isEmpty()) {
             si.errors.put("username", Messages.HudsonPrivateSecurityRealm_CreateAccount_UserNameRequired());
         } else if (!containsOnlyAcceptableCharacters(si.username)) {
             if (ID_REGEX == null) {
@@ -445,7 +445,7 @@ public class HudsonPrivateSecurityRealm extends AbstractPasswordBasedSecurityRea
             si.errors.put("password1", Messages.HudsonPrivateSecurityRealm_CreateAccount_PasswordRequired());
         }
 
-        if (si.fullname == null || si.fullname.length() == 0) {
+        if (si.fullname == null || si.fullname.isEmpty()) {
             si.fullname = si.username;
         }
 

core/src/main/java/hudson/security/csrf/CrumbFilter.java

@@ -79,7 +79,7 @@ public class CrumbFilter implements Filter {
         private static String canonicalPath(String path) {
             List<String> r = new ArrayList<>(Arrays.asList(path.split("/+")));
             for (int i = 0; i < r.size(); ) {
-                if (r.get(i).length() == 0 || r.get(i).equals(".")) {
+                if (r.get(i).isEmpty() || r.get(i).equals(".")) {
                     // empty token occurs for example, "".split("/+") is [""]
                     r.remove(i);
                 } else

core/src/main/java/hudson/slaves/AbstractCloudImpl.java

@@ -25,7 +25,7 @@ public abstract class AbstractCloudImpl extends Cloud {
     }
 
     protected void setInstanceCapStr(String value) {
-        if (value == null || value.equals(""))
+        if (value == null || value.isEmpty())
             this.instanceCap = Integer.MAX_VALUE;
         else
             this.instanceCap = Integer.parseInt(value);

core/src/main/java/hudson/tasks/ArtifactArchiver.java

@@ -236,7 +236,7 @@ public class ArtifactArchiver extends Recorder implements SimpleBuildStep {
 
     @Override
     public void perform(Run<?, ?> build, FilePath ws, EnvVars environment, Launcher launcher, TaskListener listener) throws IOException, InterruptedException {
-        if (artifacts.length() == 0) {
+        if (artifacts.isEmpty()) {
             throw new AbortException(Messages.ArtifactArchiver_NoIncludes());
         }
 

core/src/main/java/hudson/tasks/Maven.java

@@ -560,7 +560,7 @@ public class Maven extends Builder {
             // olamy : but will add a dependency on maven in core -> so not so good
             String mavenVersion = launcher.getChannel().call(new GetMavenVersion(getHome()));
 
-            if (!mavenVersion.equals("")) {
+            if (!mavenVersion.isEmpty()) {
                 if (mavenReqVersion == MAVEN_20) {
                     if (mavenVersion.startsWith("2."))
                         return true;

core/src/main/java/hudson/util/ArgumentListBuilder.java

@@ -297,7 +297,7 @@ public class ArgumentListBuilder implements Serializable, Cloneable {
         for (String arg : args) {
             if (buf.length() > 0)  buf.append(' ');
 
-            if (arg.indexOf(' ') >= 0 || arg.length() == 0)
+            if (arg.indexOf(' ') >= 0 || arg.isEmpty())
                 buf.append('"').append(arg).append('"');
             else
                 buf.append(arg);
@@ -439,7 +439,7 @@ public class ArgumentListBuilder implements Serializable, Cloneable {
 
             if (buf.length() > 0)  buf.append(' ');
 
-            if (arg.indexOf(' ') >= 0 || arg.length() == 0)
+            if (arg.indexOf(' ') >= 0 || arg.isEmpty())
                 buf.append('"').append(arg).append('"');
             else
                 buf.append(arg);

core/src/main/java/hudson/util/FormFieldValidator.java

@@ -617,7 +617,7 @@ public abstract class FormFieldValidator {
                     }
                 }
                 v = v.trim();
-                if (!allowEmpty && v.length() == 0) {
+                if (!allowEmpty && v.isEmpty()) {
                     fail();
                     return;
                 }

core/src/main/java/hudson/util/FormValidation.java

@@ -449,7 +449,7 @@ public abstract class FormValidation extends IOException implements HttpResponse
                     return error(errorMessage);
             }
             v = v.trim();
-            if (!allowEmpty && v.length() == 0)
+            if (!allowEmpty && v.isEmpty())
                 return error(errorMessage);
 
             Base64.getDecoder().decode(v.getBytes(StandardCharsets.UTF_8));
@@ -655,8 +655,8 @@ public abstract class FormValidation extends IOException implements HttpResponse
                 QueryParameter qp = p.annotation(QueryParameter.class);
                 if (qp != null) {
                     String name = qp.value();
-                    if (name.length() == 0) name = p.name();
-                    if (name == null || name.length() == 0)
+                    if (name.isEmpty()) name = p.name();
+                    if (name == null || name.isEmpty())
                         continue;   // unknown parameter name. we'll report the error when the form is submitted.
                     if (name.equals("value"))
                         continue;   // 'value' parameter is implicit

core/src/main/java/hudson/util/LineEndingConversion.java

@@ -32,7 +32,7 @@ public class LineEndingConversion {
      *     String updated with the new line endings or null if given null.
      */
     public static String convertEOL(String input, EOLType type) {
-        if (null == input || 0 == input.length()) {
+        if (null == input || input.isEmpty()) {
             return input;
         }
         // Convert line endings to Unix LF,

core/src/main/java/hudson/util/QueryParameterMap.java

@@ -56,7 +56,7 @@ public class QueryParameterMap {
      *      String that looks like {@code abc=def&ghi=jkl}
      */
     public QueryParameterMap(String queryString) {
-        if (queryString == null || queryString.length() == 0)   return;
+        if (queryString == null || queryString.isEmpty())   return;
         for (String param : queryString.split("&")) {
             String[] kv = param.split("=");
             String key = URLDecoder.decode(kv[0], StandardCharsets.UTF_8);

core/src/main/java/hudson/util/SecretRewriter.java

@@ -170,7 +170,7 @@ public class SecretRewriter {
                 if (child.isDirectory()) {
                     if (!isIgnoredDir(child))
                         rewritten += rewriteRecursive(child,
-                                relative.length() == 0 ? cn : relative + '/' + cn,
+                                relative.isEmpty() ? cn : relative + '/' + cn,
                                 listener);
                 }
             }

core/src/main/java/hudson/util/Service.java

@@ -57,7 +57,7 @@ public class Service {
                 String line;
                 while ((line = configFile.readLine()) != null) {
                     line = line.trim();
-                    if (line.startsWith("#") || line.length() == 0) continue;
+                    if (line.startsWith("#") || line.isEmpty()) continue;
 
                     try {
                         Class<?> t = classLoader.loadClass(line);
@@ -89,7 +89,7 @@ public class Service {
                         if (line.startsWith("#"))
                             continue;   // comment line
                         line = line.trim();
-                        if (line.length() == 0)
+                        if (line.isEmpty())
                             continue;   // empty line. ignore.
 
                         try {

core/src/main/java/hudson/util/jna/RegistryKey.java

@@ -52,8 +52,8 @@ public class RegistryKey implements AutoCloseable {
     }
 
     private static String combine(String a, String b) {
-        if (a.length() == 0)   return b;
-        if (b.length() == 0)   return a;
+        if (a.isEmpty())   return b;
+        if (b.isEmpty())   return a;
         return a + '\\' + b;
     }
 

core/src/main/java/jenkins/model/Jenkins.java

@@ -4229,7 +4229,7 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
      *      if the given name is not good
      */
     public static void checkGoodName(String name) throws Failure {
-        if (name == null || name.length() == 0)
+        if (name == null || name.isEmpty())
             throw new Failure(Messages.Hudson_NoName());
 
         if (".".equals(name.trim()))

core/src/main/java/jenkins/org/apache/commons/validator/routines/InetAddressValidator.java

@@ -99,7 +99,7 @@ public class InetAddressValidator implements Serializable {
 
         // verify that address subgroups are legal
         for (String ipSegment : groups) {
-            if (ipSegment == null || ipSegment.length() == 0) {
+            if (ipSegment == null || ipSegment.isEmpty()) {
                 return false;
             }
 
@@ -186,7 +186,7 @@ public class InetAddressValidator implements Serializable {
         int emptyOctets = 0; // consecutive empty chunks
         for (int index = 0; index < octets.length; index++) {
             String octet = octets[index];
-            if (octet.length() == 0) {
+            if (octet.isEmpty()) {
                 emptyOctets++;
                 if (emptyOctets > 1) {
                     return false;

core/src/main/java/jenkins/org/apache/commons/validator/routines/RegexValidator.java

@@ -131,7 +131,7 @@ public class RegexValidator implements Serializable {
         patterns = new Pattern[regexs.length];
         int flags = caseSensitive ? 0 : Pattern.CASE_INSENSITIVE;
         for (int i = 0; i < regexs.length; i++) {
-            if (regexs[i] == null || regexs[i].length() == 0) {
+            if (regexs[i] == null || regexs[i].isEmpty()) {
                 throw new IllegalArgumentException("Regular expression[" + i + "] is missing");
             }
             patterns[i] =  Pattern.compile(regexs[i], flags);

core/src/main/java/jenkins/telemetry/impl/StaplerDispatches.java

@@ -66,7 +66,7 @@ public class StaplerDispatches extends Telemetry {
 
     @Override
     public JSONObject createContent() {
-        if (traces.size() == 0) {
+        if (traces.isEmpty()) {
             return null;
         }
         Map<String, Object> info = new TreeMap<>();

core/src/main/java/jenkins/telemetry/impl/UserLanguages.java

@@ -82,7 +82,7 @@ public class UserLanguages extends Telemetry {
 
     @Override
     public JSONObject createContent() {
-        if (requestsByLanguage.size() == 0) {
+        if (requestsByLanguage.isEmpty()) {
             return null;
         }
         Map<String, AtomicLong> currentRequests = new TreeMap<>(requestsByLanguage);

core/src/main/java/jenkins/util/TreeStringBuilder.java

@@ -37,7 +37,7 @@ public class TreeStringBuilder {
          * if any.
          */
         public Child intern(final String s) {
-            if (s.length() == 0) {
+            if (s.isEmpty()) {
                 return this;
             }
 

core/src/main/java/jenkins/util/VirtualFile.java

@@ -1096,7 +1096,7 @@ public abstract class VirtualFile implements Comparable<VirtualFile>, Serializab
         @Override
         @Restricted(NoExternalUse.class)
         public boolean isDescendant(String potentialChildRelativePath) throws IOException {
-            if (potentialChildRelativePath.equals("") && cacheDescendant) {
+            if (potentialChildRelativePath.isEmpty() && cacheDescendant) {
                 return true;
             }
 

core/src/main/java/jenkins/widgets/HistoryPageFilter.java

@@ -181,7 +181,7 @@ public class HistoryPageFilter<T> {
                         break;
                     }
                 }
-                if (itemsToAdd.size() == 0) {
+                if (itemsToAdd.isEmpty()) {
                     // All builds are older than newerThan ?
                     hasDownPage = true;
                 } else {