java_泛型方法使用实例

package ming;
import java.util.ArrayList;
import java.util.Collection;

public class GenericMethodTest {

static <T> void fromArraytoCollection(T[] a, Collection<T> c) {
for (T o : a) {
c.add(o);
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
//T stand for Object
Object[] oa = new Object[100];
Collection<Object> co = new ArrayList<Object>();
fromArraytoCollection(oa,co);

//T stand for Number
Integer[] ia = new Integer[100];
Float[] fa = new Float[100];
Collection<Number> cn = new ArrayList<Number>();

fromArraytoCollection(ia,cn);
fromArraytoCollection(fa,cn);

}

}

package ming;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class GenericMethodTest {

static <T> void fromArraytoCollection(Collection<? extends T> from,
Collection<T> to) {
for (T ele : from) {
to.add(ele);
}
}

public static void main(String[] args) {
List<Object> ao = new ArrayList<Object>();
List<String> as = new ArrayList<String>();
// string is subclass of object
fromArraytoCollection(as, ao);

}

}