diff --git a/build.gradle b/build.gradle
index 8e293b06c23..19bf3cdc7ac 100644
--- a/build.gradle
+++ b/build.gradle
@@ -927,9 +927,10 @@ subprojects {
             }
           } catch (Exception ex) {
             if (ex.getCause() != null && ex.getCause().getCause()!= null) {
-              String msg = ex.getCause().getLocalizedMessage() + ':\n'
-              msg += ex.getCause().getCause().getLocalizedMessage() + '\n'
-              msg += 'Have you installed jtreg?'
+              String msg = String.join(System.lineSeparator(),
+                  ex.getCause().getLocalizedMessage() + ':',
+                  ex.getCause().getCause().getLocalizedMessage(),
+                  'Have you installed jtreg?')
               println msg
             }
             throw ex
diff --git a/checker-qual-android/build.gradle b/checker-qual-android/build.gradle
index 38ce591d55d..816f06e18b1 100644
--- a/checker-qual-android/build.gradle
+++ b/checker-qual-android/build.gradle
@@ -38,14 +38,16 @@ final checkerQualAndroidPom(publication) {
   publication.from components.java
   publication.pom {
     name = 'Checker Qual Android'
-    description = 'checker-qual-android contains annotations (type qualifiers) that a programmer\n' +
-        'writes to specify Java code for type-checking by the Checker Framework.\n' +
-        '\n' +
-        'The checker-qual-android artifact is identical to the checker-qual\n' +
-        'artifact, except that in checker-qual-android annotations have classfile\n' +
-        'retention.  The default Android Gradle plugin retains types annotated with\n' +
-        'runtime annotations in the main dex, but strips out class-retention\n' +
-        'annotations.\n'
+    description =
+        String.join(System.lineSeparator(),
+        'checker-qual-android contains annotations (type qualifiers) that a programmer',
+        'writes to specify Java code for type-checking by the Checker Framework.',
+        '',
+        'The checker-qual-android artifact is identical to the checker-qual',
+        'artifact, except that in checker-qual-android annotations have classfile',
+        'retention.  The default Android Gradle plugin retains types annotated with',
+        'runtime annotations in the main dex, but strips out class-retention',
+        'annotations.')
     licenses {
       license {
         name = 'The MIT License'
diff --git a/checker-qual/build.gradle b/checker-qual/build.gradle
index a74a851b4e0..7a575e377f9 100644
--- a/checker-qual/build.gradle
+++ b/checker-qual/build.gradle
@@ -45,8 +45,9 @@ final checkerQualPom(publication) {
   publication.from components.java
   publication.pom {
     name = 'Checker Qual'
-    description = 'checker-qual contains annotations (type qualifiers) that a programmer\n' +
-        'writes to specify Java code for type-checking by the Checker Framework.\n'
+    description = String.join(System.lineSeparator(),
+        'checker-qual contains annotations (type qualifiers) that a programmer' +
+        'writes to specify Java code for type-checking by the Checker Framework.')
     licenses {
       license {
         name = 'The MIT License'
diff --git a/checker/build.gradle b/checker/build.gradle
index 123c8f27b8d..c4159718fa6 100644
--- a/checker/build.gradle
+++ b/checker/build.gradle
@@ -1042,12 +1042,14 @@ final checkerPom(publication) {
   // Don't use publication.from components.java which would publish the skinny jar as checker.jar.
   publication.pom {
     name = 'Checker Framework'
-    description = 'The Checker Framework enhances Java\'s type system to\n' +
-        'make it more powerful and useful. This lets software developers\n' +
-        'detect and prevent errors in their Java programs.\n' +
-        'The Checker Framework includes compiler plug-ins ("checkers")\n' +
-        'that find bugs or verify their absence. It also permits you to\n' +
-        'write your own compiler plug-ins.'
+    description =
+        String.join(System.lineSeparator(),
+        'The Checker Framework enhances Java\'s type system to',
+        'make it more powerful and useful. This lets software developers',
+        'detect and prevent errors in their Java programs.',
+        'The Checker Framework includes compiler plug-ins ("checkers")',
+        'that find bugs or verify their absence. It also permits you to',
+        'write your own compiler plug-ins.')
     licenses {
       license {
         name = 'GNU General Public License, version 2 (GPL2), with the classpath exception'
diff --git a/checker/src/main/java/org/checkerframework/checker/resourceleak/messages.properties b/checker/src/main/java/org/checkerframework/checker/resourceleak/messages.properties
index c5776fbf9a5..a9df3c24711 100644
--- a/checker/src/main/java/org/checkerframework/checker/resourceleak/messages.properties
+++ b/checker/src/main/java/org/checkerframework/checker/resourceleak/messages.properties
@@ -1,12 +1,12 @@
-required.method.not.called=@MustCall %s may not have been invoked on %s or any of its aliases.\nThe type of object is: %s.\nReason for going out of scope: %s
+required.method.not.called=@MustCall %s may not have been invoked on %s or any of its aliases.%nThe type of object is: %s.%nReason for going out of scope: %s
 missing.creates.mustcall.for=Method %s re-assigns the non-final, owning field %s.%s, but does not have a corresponding @CreatesMustCallFor annotation.
 incompatible.creates.mustcall.for=Method %s re-assigns the non-final, owning field %s.%s, but its @CreatesMustCallFor annotation targets %s.
 reset.not.owning=Calling method %s resets the must-call obligations of the expression %s, which is non-owning. Either annotate its declaration with an @Owning annotation, extract it into a local variable, or write a corresponding @CreatesMustCallFor annotation on the method that encloses this statement.
-creates.mustcall.for.override.invalid=Method %s cannot override method %s, which defines fewer @CreatesMustCallFor targets.\nfound:    %s\nrequired: %s
+creates.mustcall.for.override.invalid=Method %s cannot override method %s, which defines fewer @CreatesMustCallFor targets.%nfound:    %s%nrequired: %s
 creates.mustcall.for.invalid.target=Cannot create a must-call obligation for "%s" since its type %s has no must-call methods.
-destructor.exceptional.postcondition=Method %s must resolve the must-call obligations of the owning field %s along all paths, including exceptional paths. On an exceptional path, the @EnsuresCalledMethods annotation was not satisfied.\nFound:    %s\nRequired: %s
-mustcallalias.out.of.scope=This @MustCallAlias parameter might go out of scope without being assigned into an owning field of this object (if this is a constructor) or returned.\nReason for going out of scope: %s
-mustcallalias.method.return.and.param=@MustCallAlias annotations must appear in pairs (one on a return type and one on a parameter type).\nBut %s
-owning.override.param=Incompatible ownership for parameter %s.\nfound   : no ownership annotation or @NotOwning\nrequired: @Owning\nConsequence: method %s in %s cannot override method %s in %s
-owning.override.return=Incompatible ownership for return.\nfound   : no ownership annotation or @Owning\nrequired: @NotOwning\nConsequence: method %s in %s cannot override method %s in %s
-required.method.not.known=The checker cannot determine the must call methods of %s or any of its aliases, so it could not determine if they were called. Typically, this error indicates that you need to write an @MustCall annotation (often on an unconstrained generic type).\nThe type of object is: %s.\nReason for going out of scope: %s
+destructor.exceptional.postcondition=Method %s must resolve the must-call obligations of the owning field %s along all paths, including exceptional paths. On an exceptional path, the @EnsuresCalledMethods annotation was not satisfied.%nFound:    %s%nRequired: %s
+mustcallalias.out.of.scope=This @MustCallAlias parameter might go out of scope without being assigned into an owning field of this object (if this is a constructor) or returned.%nReason for going out of scope: %s
+mustcallalias.method.return.and.param=@MustCallAlias annotations must appear in pairs (one on a return type and one on a parameter type).%nBut %s
+owning.override.param=Incompatible ownership for parameter %s.%nfound   : no ownership annotation or @NotOwning%nrequired: @Owning%nConsequence: method %s in %s cannot override method %s in %s
+owning.override.return=Incompatible ownership for return.%nfound   : no ownership annotation or @Owning%nrequired: @NotOwning%nConsequence: method %s in %s cannot override method %s in %s
+required.method.not.known=The checker cannot determine the must call methods of %s or any of its aliases, so it could not determine if they were called. Typically, this error indicates that you need to write an @MustCall annotation (often on an unconstrained generic type).%nThe type of object is: %s.%nReason for going out of scope: %s
diff --git a/dataflow/build.gradle b/dataflow/build.gradle
index 8127ddfaa41..b23e410b157 100644
--- a/dataflow/build.gradle
+++ b/dataflow/build.gradle
@@ -187,11 +187,13 @@ final dataflowShadedPom(MavenPublication publication, String shadedPkgName) {
   publication.artifactId = "dataflow-${shadedPkgName}"
   publication.pom {
     name = "Dataflow (${shadedPkgName})"
-    description = "dataflow-${shadedPkgName} is a dataflow framework based on the javac compiler.\n" +
-        '\n' +
-        'It differs from the org.checkerframework:dataflow artifact in two ways.\n' +
-        "First, the packages in this artifact have been renamed to org.checkerframework.${shadedPkgName}.*.\n" +
-        'Second, unlike the dataflow artifact, this artifact contains the dependencies it requires.'
+    description =
+        String.join(System.lineSeparator(),
+        "dataflow-${shadedPkgName} is a dataflow framework based on the javac compiler.",
+        '',
+        'It differs from the org.checkerframework:dataflow artifact in two ways.',
+        "First, the packages in this artifact have been renamed to org.checkerframework.${shadedPkgName}.*.",
+        'Second, unlike the dataflow artifact, this artifact contains the dependencies it requires.')
     licenses {
       license {
         name = 'GNU General Public License, version 2 (GPL2), with the classpath exception'
diff --git a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/AbstractCFGVisualizer.java b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/AbstractCFGVisualizer.java
index b5a8254ad73..cfdb28afe1f 100644
--- a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/AbstractCFGVisualizer.java
+++ b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/AbstractCFGVisualizer.java
@@ -192,8 +192,8 @@ protected void addBlock(Block b, Set<Block> visited, Queue<Block> workList) {
    * @param bb the block
    * @param analysis the current analysis
    * @param separator the line separator. Examples: "\\l" for left justification in {@link
-   *     DOTCFGVisualizer} (this is really a terminator, not a separator), "\n" to add a new line in
-   *     {@link StringCFGVisualizer}
+   *     DOTCFGVisualizer} (this is really a terminator, not a separator), "\n" or {@code
+   *     System.lineSeparator()} to add a new line in {@link StringCFGVisualizer}
    * @return the String representation of the block
    */
   protected String visualizeBlockWithSeparator(
@@ -296,8 +296,8 @@ protected enum VisualizeWhere {
    * @param bb a block
    * @param analysis the current analysis
    * @param separator the line separator. Examples: "\\l" for left justification in {@link
-   *     DOTCFGVisualizer} (which is actually a line TERMINATOR, not a separator!), "\n" to add a
-   *     new line in {@link StringCFGVisualizer}
+   *     DOTCFGVisualizer} (which is actually a line TERMINATOR, not a separator!), "\n" or {@code
+   *     System.lineSeparator()} to add a new line in {@link StringCFGVisualizer}
    * @return the visualization of the transfer input before or after the given block
    */
   protected String visualizeBlockTransferInputHelper(
diff --git a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/CFGVisualizeLauncher.java b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/CFGVisualizeLauncher.java
index e7f149b99a4..beedf9ccb27 100644
--- a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/CFGVisualizeLauncher.java
+++ b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/CFGVisualizeLauncher.java
@@ -286,7 +286,7 @@ public static void writeStringOfCFG(
       if (res != null && res.get("stringGraph") != null) {
         out.write(res.get("stringGraph").toString());
       }
-      out.write("\n");
+      out.write(System.lineSeparator());
     } catch (IOException e) {
       e.printStackTrace();
     }
diff --git a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/StringCFGVisualizer.java b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/StringCFGVisualizer.java
index 9ee7882bcbe..0f47ce3257c 100644
--- a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/StringCFGVisualizer.java
+++ b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/visualize/StringCFGVisualizer.java
@@ -48,7 +48,7 @@ public void init(Map<String, Object> args) {
 
   @Override
   public String getSeparator() {
-    return "\n";
+    return System.lineSeparator();
   }
 
   @Override
diff --git a/framework-test/build.gradle b/framework-test/build.gradle
index f1b6fdc87c9..9d09a7b280c 100644
--- a/framework-test/build.gradle
+++ b/framework-test/build.gradle
@@ -23,8 +23,9 @@ final frameworkTest(publication) {
   publication.from components.java
   publication.pom {
     name = 'Checker Framework Testing Library'
-    description = 'framework-test contains utility classes for testing type-checkers\n' +
-        'that are built on the Checker Framework.'
+    description = String.join(System.lineSeparator(),
+        'framework-test contains utility classes for testing type-checkers' +
+        'that are built on the Checker Framework.')
     licenses {
       license {
         name = 'GNU General Public License, version 2 (GPL2), with the classpath exception'
diff --git a/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java b/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java
index 342d8366227..6ab1a194f65 100644
--- a/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java
+++ b/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java
@@ -487,12 +487,9 @@ protected void testAnnotationInsertion() {
 
     String withAnnotations;
     try (InputStream annotationInputStream = root.getSourceFile().openInputStream()) {
-      // This check only runs on files from the Checker Framework test suite, which should all
-      // use UNIX line separators. Using System.lineSeparator instead of "\n" could cause the
-      // test to fail on Mac or Windows.
       withAnnotations =
           new InsertAjavaAnnotations(elements)
-              .insertAnnotations(annotationInputStream, withoutAnnotations, "\n");
+              .insertAnnotations(annotationInputStream, withoutAnnotations, System.lineSeparator());
     } catch (IOException e) {
       throw new BugInCF("Error while reading Java file: " + root.getSourceFile().toUri(), e);
     }
@@ -501,7 +498,7 @@ protected void testAnnotationInsertion() {
     try {
       modifiedAst = JavaParserUtil.parseCompilationUnit(withAnnotations);
     } catch (ParseProblemException e) {
-      throw new BugInCF("Failed to parse code after annotation insertion:\n" + withAnnotations, e);
+      throw new BugInCF("Failed to parse code after annotation insertion: " + withAnnotations, e);
     }
 
     AnnotationEqualityVisitor visitor = new AnnotationEqualityVisitor();
diff --git a/framework/src/main/java/org/checkerframework/common/wholeprograminference/WholeProgramInferenceImplementation.java b/framework/src/main/java/org/checkerframework/common/wholeprograminference/WholeProgramInferenceImplementation.java
index cb219896892..e19422d3bff 100644
--- a/framework/src/main/java/org/checkerframework/common/wholeprograminference/WholeProgramInferenceImplementation.java
+++ b/framework/src/main/java/org/checkerframework/common/wholeprograminference/WholeProgramInferenceImplementation.java
@@ -327,7 +327,7 @@ private void updateInferredExecutableParameterTypes(
         if (showWpiFailedInferences) {
           printFailedInferenceDebugMessage(
               "Annotations cannot be placed on varargs parameters in -Ainfer=jaifs mode, because"
-                  + " the JAIF format does not correctly support it.\n"
+                  + " the JAIF format does not correctly support it. "
                   + "The signature of the method whose varargs parameter was not annotated is: "
                   + JVMNames.getJVMMethodSignature(methodElt));
         }
@@ -363,7 +363,7 @@ private void updateInferredExecutableParameterTypes(
               printFailedInferenceDebugMessage(
                   "Javac cannot create an array type "
                       + "from a wildcard, so WPI did not attempt to infer a type for an array "
-                      + "parameter.\n"
+                      + "parameter. "
                       + "The signature of the method whose parameter had inference skipped is: "
                       + JVMNames.getJVMMethodSignature(methodElt));
             }
@@ -594,7 +594,7 @@ public void updateFromFormalParameterAssignment(
         printFailedInferenceDebugMessage(
             "Could not update from formal parameter "
                 + "assignment, because an ArrayCreationNode with a null tree is created when "
-                + "the parameter is a variable-length list.\nParameter: "
+                + "the parameter is a variable-length list. Parameter: "
                 + paramElt);
       }
       return;
@@ -613,7 +613,7 @@ public void updateFromFormalParameterAssignment(
         printFailedInferenceDebugMessage(
             "Could not update from formal "
                 + "parameter assignment inside a lambda expression, because lambda parameters "
-                + "cannot be annotated.\nParameter: "
+                + "cannot be annotated. Parameter: "
                 + paramElt);
       }
       return;
@@ -1101,12 +1101,12 @@ public void updateAtmWithLub(AnnotatedTypeMirror sourceCodeATM, AnnotatedTypeMir
         } else {
           if (showWpiFailedInferences) {
             printFailedInferenceDebugMessage(
-                "attempted to update the component type of an array type, but found an unexpected"
-                    + " difference in type structure.\n"
-                    + "LHS kind: "
-                    + sourceCodeComponent.getKind()
-                    + "\nRHS kind: "
-                    + ajavaComponent.getKind());
+                String.join(
+                    System.lineSeparator(),
+                    "attempted to update the component type of an array type, but found an"
+                        + " unexpected difference in type structure.",
+                    "LHS kind: " + sourceCodeComponent.getKind(),
+                    "RHS kind: " + ajavaComponent.getKind()));
             break;
           }
         }
diff --git a/framework/src/main/java/org/checkerframework/framework/source/SourceChecker.java b/framework/src/main/java/org/checkerframework/framework/source/SourceChecker.java
index a87d3694192..23622dd1ab4 100644
--- a/framework/src/main/java/org/checkerframework/framework/source/SourceChecker.java
+++ b/framework/src/main/java/org/checkerframework/framework/source/SourceChecker.java
@@ -1316,9 +1316,9 @@ protected void printOrStoreMessage(
    */
   private void printStackTrace(StackTraceElement[] trace) {
     if (hasOption("dumpOnErrors")) {
-      StringBuilder msg = new StringBuilder();
+      StringJoiner msg = new StringJoiner(System.lineSeparator());
       for (StackTraceElement elem : trace) {
-        msg.append("\tat " + elem + "\n");
+        msg.add("\tat " + elem);
       }
       message(Diagnostic.Kind.NOTE, msg.toString());
     }
diff --git a/framework/src/main/java/org/checkerframework/framework/util/typeinference8/types/InferenceFactory.java b/framework/src/main/java/org/checkerframework/framework/util/typeinference8/types/InferenceFactory.java
index 982a019726e..f21b0c89511 100644
--- a/framework/src/main/java/org/checkerframework/framework/util/typeinference8/types/InferenceFactory.java
+++ b/framework/src/main/java/org/checkerframework/framework/util/typeinference8/types/InferenceFactory.java
@@ -183,7 +183,7 @@ public InferenceFactory(Java8InferenceContext context) {
           return new ProperType(res, TreeUtils.typeOf(var), this.context);
         } else {
           throw new BugInCF(
-              "Unexpected assignment context.\nKind: %s\nTree: %s", context.getKind(), context);
+              "Unexpected assignment context.%nKind: %s%nTree: %s", context.getKind(), context);
         }
     }
   }