jdk里经典的泛型用法 

java.util.Arrays
java.util.Collections 
java.util.HashMap



java.util.HashMap


public class HashMap<K,V> extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable
    
static class Node<K,V> implements Map.Entry<K,V> {
        final int hash;
        final K key;
        V value;
        Node<K,V> next;
        
public V put(K key, V value)

public void putAll(Map<? extends K, ? extends V> m)
 
public V get(Object key) 
 
public Set<K> keySet()

public Collection<V> values()

public Set<Map.Entry<K,V>> entrySet()






java.util.Arrays



public static <T> List<T> asList(T... a) {
    return new ArrayList<>(a);
}

public static <T> int binarySearch(T[] a, T key, Comparator<? super T> c) {
    return binarySearch0(a, 0, a.length, key, c);
}   
    
public static <T> T[] copyOfRange(T[] original, int from, int to)

public static <T> void sort(T[] a, Comparator<? super T> c)

public static <T> Stream<T> stream(T[] array) 


public static <T,U> T[] copyOf(U[] original, int newLength, Class<? extends T[]> newType) {
        @SuppressWarnings("unchecked")
        T[] copy = ((Object)newType == (Object)Object[].class)
            ? (T[]) new Object[newLength]
            : (T[]) Array.newInstance(newType.getComponentType(), newLength);
        System.arraycopy(original, 0, copy, 0,
                         Math.min(original.length, newLength));
        return copy;
}
    
public static <T> void parallelSort(T[] a, Comparator<? super T> cmp) 
    
    




java.util.Collections 


public static final <T> List<T> emptyList() {
        return (List<T>) EMPTY_LIST;
}

public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll)

public static <T> void sort(List<T> list, Comparator<? super T> c) 

public static <T> int binarySearch(List<? extends Comparable<? super T>> list, T key)
    
public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) 

public static void reverse(List<?> list) 
 

public static <T> List<T> singletonList(T o) {
        return new SingletonList<>(o);
}

public static <T> List<T> synchronizedList(List<T> list)
  
public static <T> List<T> unmodifiableList(List<? extends T> list) 

 



 java泛型  
 java泛型技巧