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javagenericsgeneric-function

Use methods inside a generic type

Consider this class:

public class A {
   public void method_a(){
       System.out.println("THIS IS IT");
 }
}

I want to use 'method_a' in another function using generic type to get class A. for example:

public class B {
    public void calling_this(){
        A = new A();
        method_b(A);
    }
    public <T> void method_b(T m){
        m.method_a();
    }
}

I get error "cannot find symbol" on m.method_a(). Is this method possible or is there any thing like equivalent to it?

Solution

  • With generics you can set some restrictions

    interface HasMethodA {
    void method_a();
}

...

class ... {

    <T extends HasMethodA> ... (..., T hasMethodA, ...) {
        ...
        hasMethodA.method_a();
        ...
    }

}

    See Bounded Type Parameters