get class from generic type java
class Foo<T> {
final Class<T> typeParameterClass;
public Foo(Class<T> typeParameterClass) {
this.typeParameterClass = typeParameterClass;
}
public void bar() {
// you can access the typeParameterClass here and do whatever you like
}java generic type method
// generic methods
public <T> List<T> fromArrayToList(T[] a) {
return Arrays.stream(a).collect(Collectors.toList());
}
public static <T, G> List<G> fromArrayToList(T[] a, Function<T, G> mapperFunction) {
return Arrays.stream(a)
.map(mapperFunction)
.collect(Collectors.toList());
}
// bounded generics
public <T extends Number> List<T> fromArrayToList(T[] a) {
...
}
//multiple bounds
<T extends Number & Comparable>
// upper bound wildcards
public static void paintAllBuildings(List<? extends Building> buildings) {
...
}
// lower bound wildcard
<? super T>generic class java
public interface Pair<K, V> {
public K getKey();
public V getValue();
}
public class OrderedPair<K, V> implements Pair<K, V> {
private K key;
private V value;
public OrderedPair(K key, V value) {
this.key = key;
this.value = value;
}
public K getKey() { return key; }
public V getValue() { return value; }
}java define a generic class that produces
List list = new ArrayList();
list.add("abc");
list.add(new Integer(5)); //OK
for(Object obj : list){
//type casting leading to ClassCastException at runtime
String str=(String) obj;
}Copyright © 2021 Codeinu
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