Return type question

[Herland Cid]

Studying for this exam, I have a return type question. I don't understand why Fig 1 is illegal but Fig 2 is legal, any hints? thanks

Fig 1:

public class Foo{
void go(){ }
}

public class Bar extends Foo {
String go () { //Illegal code
return null;
}

}

------
Fig 2:

class Alpha {
Alpha doStuff(char c) {
return new Alpha();
}
}

class Beta extends Alpha {
Beta doStuff(char c) { // legal override in Java 1.5
return new Beta();
}
}

[Himai Minh]

public class Foo{ 
void go(){ } 
} 

public class Bar extends Foo { 
String go () { //Illegal code 
return null; 
} 

} 

Bar overrides go in Foo. When a method overrides another method, overriding method's return type should be the same as or subtype of that of the overriden method.

class Alpha { 
Alpha doStuff(char c) { 
return new Alpha(); 
} 
} 

class Beta extends Alpha { 
Beta doStuff(char c) { // legal override in Java 1.5 
return new Beta(); 
} 
} 

Yes, since JDK 1.5, overriding method can have the return type , which is a subtype of the return type in the overriden method.