6915171: Clarify checked/unchecked status of Throwable and its subclasses

Reviewed-by: dholmes

src/share/classes/java/lang/Error.java

@@ -26,27 +26,31 @@
 package java.lang;
 
 /**
- * An <code>Error</code> is a subclass of <code>Throwable</code>
+ * An {@code Error} is a subclass of {@code Throwable}
  * that indicates serious problems that a reasonable application
  * should not try to catch. Most such errors are abnormal conditions.
- * The <code>ThreadDeath</code> error, though a "normal" condition,
- * is also a subclass of <code>Error</code> because most applications
+ * The {@code ThreadDeath} error, though a "normal" condition,
+ * is also a subclass of {@code Error} because most applications
  * should not try to catch it.
  * <p>
- * A method is not required to declare in its <code>throws</code>
- * clause any subclasses of <code>Error</code> that might be thrown
+ * A method is not required to declare in its {@code throws}
+ * clause any subclasses of {@code Error} that might be thrown
  * during the execution of the method but not caught, since these
  * errors are abnormal conditions that should never occur.
  *
+ * That is, {@code Error} and its subclasses are regarded as unchecked
+ * exceptions for the purposes of compile-time checking of exceptions.
+ *
  * @author  Frank Yellin
  * @see     java.lang.ThreadDeath
+ * @jls3 11.2 Compile-Time Checking of Exceptions
  * @since   JDK1.0
  */
 public class Error extends Throwable {
     static final long serialVersionUID = 4980196508277280342L;
 
     /**
-     * Constructs a new error with <code>null</code> as its detail message.
+     * Constructs a new error with {@code null} as its detail message.
      * The cause is not initialized, and may subsequently be initialized by a
      * call to {@link #initCause}.
      */
@@ -69,7 +73,7 @@ public class Error extends Throwable {
     /**
      * Constructs a new error with the specified detail message and
      * cause.  <p>Note that the detail message associated with
-     * <code>cause</code> is <i>not</i> automatically incorporated in
+     * {@code cause} is <i>not</i> automatically incorporated in
      * this error's detail message.
      *
      * @param  message the detail message (which is saved for later retrieval

src/share/classes/java/lang/Exception.java

@@ -26,19 +26,27 @@
 package java.lang;
 
 /**
- * The class <code>Exception</code> and its subclasses are a form of
- * <code>Throwable</code> that indicates conditions that a reasonable
+ * The class {@code Exception} and its subclasses are a form of
+ * {@code Throwable} that indicates conditions that a reasonable
  * application might want to catch.
  *
+ * <p>The class {@code Exception} and any subclasses that are not also
+ * subclasses of {@link RuntimeException} are <em>checked
+ * exceptions</em>.  Checked exceptions need to be declared in a
+ * method or constructor's {@code throws} clause if they can be thrown
+ * by the execution of the method or constructor and propagate outside
+ * the method or constructor boundary.
+ *
  * @author  Frank Yellin
  * @see     java.lang.Error
+ * @jls3 11.2 Compile-Time Checking of Exceptions
  * @since   JDK1.0
  */
 public class Exception extends Throwable {
     static final long serialVersionUID = -3387516993124229948L;
 
     /**
-     * Constructs a new exception with <code>null</code> as its detail message.
+     * Constructs a new exception with {@code null} as its detail message.
      * The cause is not initialized, and may subsequently be initialized by a
      * call to {@link #initCause}.
      */
@@ -61,7 +69,7 @@ public class Exception extends Throwable {
     /**
      * Constructs a new exception with the specified detail message and
      * cause.  <p>Note that the detail message associated with
-     * <code>cause</code> is <i>not</i> automatically incorporated in
+     * {@code cause} is <i>not</i> automatically incorporated in
      * this exception's detail message.
      *
      * @param  message the detail message (which is saved for later retrieval

src/share/classes/java/lang/RuntimeException.java

@@ -26,22 +26,24 @@
 package java.lang;
 
 /**
- * <code>RuntimeException</code> is the superclass of those
+ * {@code RuntimeException} is the superclass of those
  * exceptions that can be thrown during the normal operation of the
  * Java Virtual Machine.
- * <p>
- * A method is not required to declare in its <code>throws</code>
- * clause any subclasses of <code>RuntimeException</code> that might
- * be thrown during the execution of the method but not caught.
  *
+ * <p>{@code RuntimeException} and its subclasses are <em>unchecked
+ * exceptions</em>.  Unchecked exceptions do <em>not</em> need to be
+ * declared in a method or constructor's {@code throws} clause if they
+ * can be thrown by the execution of the method or constructor and
+ * propagate outside the method or constructor boundary.
  *
  * @author  Frank Yellin
+ * @jls3 11.2 Compile-Time Checking of Exceptions
  * @since   JDK1.0
  */
 public class RuntimeException extends Exception {
     static final long serialVersionUID = -7034897190745766939L;
 
-    /** Constructs a new runtime exception with <code>null</code> as its
+    /** Constructs a new runtime exception with {@code null} as its
      * detail message.  The cause is not initialized, and may subsequently be
      * initialized by a call to {@link #initCause}.
      */
@@ -63,7 +65,7 @@ public class RuntimeException extends Exception {
     /**
      * Constructs a new runtime exception with the specified detail message and
      * cause.  <p>Note that the detail message associated with
-     * <code>cause</code> is <i>not</i> automatically incorporated in
+     * {@code cause} is <i>not</i> automatically incorporated in
      * this runtime exception's detail message.
      *
      * @param  message the detail message (which is saved for later retrieval

src/share/classes/java/lang/Throwable.java

@@ -34,6 +34,11 @@ import  java.io.*;
  * this class or one of its subclasses can be the argument type in a
  * <code>catch</code> clause.
  *
+ * For the purposes of compile-time checking of exceptions, {@code
+ * Throwable} and any subclass of {@code Throwable} that is not also a
+ * subclass of either {@link RuntimeException} or {@link Error} are
+ * regarded as checked exceptions.
+ *
  * <p>Instances of two subclasses, {@link java.lang.Error} and
  * {@link java.lang.Exception}, are conventionally used to indicate
  * that exceptional situations have occurred. Typically, these instances
@@ -142,6 +147,7 @@ import  java.io.*;
  * @author  unascribed
  * @author  Josh Bloch (Added exception chaining and programmatic access to
  *          stack trace in 1.4.)
+ * @jls3 11.2 Compile-Time Checking of Exceptions
  * @since JDK1.0
  */
 public class Throwable implements Serializable {