http://stackoverflow.com/questions/8422842/in-java-syntax-class-extends-something
There are a few confusing answers here so I will try and clear this up. You define a generic as such:
public class Foo<T> {
private T t;
public void setValue(T t) {
this.t = t;
}
public T getValue() {
return t;
}
}If you want a generic on Foo to always extend a class Bar you would declare it as such:
public class Foo<T extends Bar> {
private T t;
public void setValue(T t) {
this.t = t;
}
public T getValue() {
return t;
}
}The ? is used when you declare a variable.
Foo<? extends Bar>foo = getFoo();OR
DoSomething(List<? extends Bar> listOfBarObjects) {
//internals
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