$ cat -n Tiger.java
     1 class Super {
     2 Number method() {
     3 return 1;
     4 }
     5 }
     6
     7 class Tiger extends Super {
     8 Integer method() {
     9 return 1;
    10 }
    11 }
$ cat -n Mantis1.java
     1 class Mantis1 extends Tiger {
     2 Integer method() {
     3 return new Integer(1);
     4 }
     5 }
$ cat -n Mantis2.java
     1 class Mantis2 extends Tiger {
     2 Number method() {
     3 return new Integer(1);
     4 }
     5 }
$ /usr/java/jdk1.5.0/bin/javac -J-showversion -sourcepath /xyz Tiger.java
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-b64)
Java HotSpot(TM) Client VM (build 1.5.0-b64, mixed mode, sharing)
 
$ /usr/java/jdk1.5.0/bin/javac -J-showversion -sourcepath /xyz -source 1.4 Mantis1.java
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-b64)
Java HotSpot(TM) Client VM (build 1.5.0-b64, mixed mode, sharing)
 
Mantis1.java:2: warning: method() in Mantis1 overrides method() in Tiger; overridden method is a bridge method
    Integer method() {
            ^
Mantis1.java:2: method() in Mantis1 cannot override method() in Tiger; attempting to use incompatible return type
found : java.lang.Integer
required: java.lang.Number
    Integer method() {
            ^
1 error
1 warning
$ /usr/java/jdk1.5.0/bin/javac -J-showversion -sourcepath /xyz -source 1.4 Mantis2.java
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-b64)
Java HotSpot(TM) Client VM (build 1.5.0-b64, mixed mode, sharing)
 
Mantis2.java:2: warning: method() in Mantis2 overrides method() in Tiger; overridden method is a bridge method
    Number method() {
           ^
Mantis2.java:2: method() in Mantis2 cannot override method() in Tiger; attempting to use incompatible return type
found : java.lang.Number
required: java.lang.Integer
    Number method() {
           ^
1 error
1 warning

###@###.### 2005-04-11 21:54:00 GMT