类型迁移

int f;
void bar(int i) {}
void foo() {
    bar(f);
}

String f;
void bar(String i) {}
void foo() {
    bar(f);
}

interface I<T> {
    T foo(T t);
}

class A implements I<String> {
    String myString;
    public String foo(final String s) {
        if (s == null) {
            return
               myString;
        }
        return s;
    }
}

interface I<T> {
    T foo(T t);
}

class A implements I<Integer> {
    Integer myString;
    public Integer foo(final Integer s) {
        if (s == null) {
            return
               myString;
        }
        return s;
    }
}

public class ResultContainer {
    private ArrayList<String> myResult;
    public String[] getResult() {
        return myResult.toArray(new String[myResult.size()]);
    }
}

public class ResultContainer {
    private String[] myResult;
    public String[] getResult() {
        return myResult;
    }
}