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java 泛型深入之Set有用工具 各种集合泛型深入使用演示样例,匿名内部类、内部类应用于泛型探讨
//Sets.java package org.rui.generics.set; import java.util.HashSet; import java.util.Set; /** * 一个Set有用工具 * @author lenovo * */ public class Sets { public static<T> Set<T> union(Set<T> a,Set<T> b) { Set<T> result=new HashSet<T>(a); result.addAll(b); return result; } //保留 同样 public static <T> Set<T> intersection(Set<T> a,Set<T> b) { Set<T> result=new HashSet<T>(a); result.retainAll(b); return result; } // 差值 //去掉同样 public static <T> Set<T> difference(Set<T> a,Set<T> b) { Set<T> result=new HashSet<T>(a); result.removeAll(b); return result; } //除了交集之外的全部过犹元素 public static <T> Set<T> complement(Set<T> a,Set<T> b) { return difference(union(a,b),intersection(a,b)); } public static void main(String[] args) { Set<String> result=new HashSet<String>(); result.add("a"); result.add("b"); Set<String> result2=new HashSet<String>(); result2.add("b"); Set<String> results=complement(result,result2); for(String s:results){ System.out.println(s); } } }
//Watercolors.java package org.rui.generics.set; //水彩画 public enum Watercolors { ZINC,LEMON_TYLLOW,MEDIUM_YELLOW,DEEP_YELLOW,ORANGE, BRILLIANT_RED }
//WatercolorSets.java package org.rui.generics.set; import java.util.EnumSet; import java.util.Set; /** * EnumSet 使用演示样例 * @author lenovo * */ public class WatercolorSets { public static void main(String[] args) { Set<Watercolors> set1=EnumSet.range( Watercolors.LEMON_TYLLOW, Watercolors.ORANGE ); Set<Watercolors> set2=EnumSet.range( Watercolors.ZINC, Watercolors.MEDIUM_YELLOW); System.out.println(set1); System.out.println(set2); //union System.out.println(" union 1 2:" +Sets.union(set1, set2)); //intersection System.out.println("intersection:"+Sets.intersection(set1, set2)); //difference 差异 System.out.println("difference1:"+Sets.difference(set1, set2)); System.out.println("difference2:"+Sets.difference(set2, set1)); //complement补足 System.out.println("complement:"+Sets.complement(set1, set2)); } }
//Watercolors.java package org.rui.generics.set; import java.lang.reflect.Method; import java.util.*; /** * 我们能够从输出中看到各种关系运算的结果 * * @author lenovo * */ public class ContainerMethodDifferences { static Set<String> methodSet(Class<?> type) { Set<String> result =new TreeSet<String>(); for(Method m:type.getMethods()) result.add(m.getName()); return result; } static void interfaces(Class<?> type) { System.out.println("interfaces in:"+type.getSimpleName()); List<String> result=new ArrayList<String>(); for(Class<?> c:type.getInterfaces()) result.add(c.getSimpleName()); System.out.println("result:"+result); } static Set<String> object=methodSet(Object.class); static{object.add("clone");} //difference static void difference(Class<?> superset,Class<?> subset) { System.out.println(superset.getSimpleName()+ " extends:"+subset.getSimpleName()); Set<String> comp=Sets.difference( methodSet(superset), methodSet(subset)); comp.removeAll(object); System.out.println("object:"+comp); interfaces(superset); } //mian public static void main(String[] args) { /*System.out.println("collection:"+ methodSet(Collection.class)); interfaces(Collections.class);*/ System.out.println("----Set-----------------------------"); difference(Set.class,Collections.class); System.out.println("----HashSet-----------------------------"); difference(HashSet.class,Set.class); System.out.println("----LinkedHashSet-----------------------------"); difference(LinkedHashSet.class,HashSet.class); System.out.println("----TreeSet-----------------------------"); difference(TreeSet.class,Set.class); System.out.println("-----List----------------------------"); difference(List.class,Collection.class); System.out.println("------ArrayList---------------------------"); difference(ArrayList.class,List.class); System.out.println("------LinkedList---------------------------"); difference(LinkedList.class,List.class); System.out.println("------Queue---------------------------"); difference(Queue.class,Collection.class); System.out.println("------PriorityQueue---------------------------"); difference(PriorityQueue.class,Queue.class); System.out.println("Map:"+methodSet(Map.class)); System.out.println("------HashMap---------------------------"); difference(HashMap.class,Map.class); System.out.println("------LinkedHashMap---------------------------"); difference(LinkedHashMap.class,HashMap.class); System.out.println("------TreeMap---------------------------"); difference(TreeMap.class,Map.class); //分类 System.out.println("------SortedMap---------------------------"); difference(SortedMap.class,Map.class); } }/*output: ----Set----------------------------- Set extends:Collections object:[toArray, iterator, remove, containsAll, contains, add, size, clear, isEmpty, retainAll, removeAll] interfaces in:Set result:[Collection] ----HashSet----------------------------- HashSet extends:Set object:[] interfaces in:HashSet result:[Set, Cloneable, Serializable] ----LinkedHashSet----------------------------- LinkedHashSet extends:HashSet object:[] interfaces in:LinkedHashSet result:[Set, Cloneable, Serializable] ----TreeSet----------------------------- TreeSet extends:Set object:[lower, last, higher, descendingIterator, subSet, pollLast, comparator, pollFirst, floor, headSet, ceiling, tailSet, first, descendingSet] interfaces in:TreeSet result:[NavigableSet, Cloneable, Serializable] -----List---------------------------- List extends:Collection object:[get, set, listIterator, lastIndexOf, indexOf, subList] interfaces in:List result:[Collection] ------ArrayList--------------------------- ArrayList extends:List object:[trimToSize, ensureCapacity] interfaces in:ArrayList result:[List, RandomAccess, Cloneable, Serializable] ------LinkedList--------------------------- LinkedList extends:List object:[offerFirst, removeFirstOccurrence, pop, peekLast, push, descendingIterator, poll, peek, removeFirst, pollLast, getFirst, offerLast, element, removeLast, offer, pollFirst, addLast, addFirst, peekFirst, getLast, removeLastOccurrence] interfaces in:LinkedList result:[List, Deque, Cloneable, Serializable] ------Queue--------------------------- Queue extends:Collection object:[element, offer, poll, peek] interfaces in:Queue result:[Collection] ------PriorityQueue--------------------------- PriorityQueue extends:Queue object:[comparator] interfaces in:PriorityQueue result:[Serializable] Map:[clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values] ------HashMap--------------------------- HashMap extends:Map object:[] interfaces in:HashMap result:[Map, Cloneable, Serializable] ------LinkedHashMap--------------------------- LinkedHashMap extends:HashMap object:[] interfaces in:LinkedHashMap result:[Map] ------TreeMap--------------------------- TreeMap extends:Map object:[pollLastEntry, firstKey, floorEntry, ceilingEntry, lowerEntry, lastEntry, subMap, tailMap, navigableKeySet, higherEntry, lowerKey, headMap, firstEntry, comparator, descendingKeySet, descendingMap, pollFirstEntry, lastKey, higherKey, floorKey, ceilingKey] interfaces in:TreeMap result:[NavigableMap, Cloneable, Serializable] ------SortedMap--------------------------- SortedMap extends:Map object:[tailMap, firstKey, headMap, comparator, lastKey, subMap] interfaces in:SortedMap result:[Map] */
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//Generator.java package org.rui.generics.anonymity; public interface Generator<T> { //返回泛型的内型对象 T next(); }
//Generators.java package org.rui.generics.anonymity; import java.util.Collection; /** * 利用生成器非常方便的填充一个collection * @author lenovo * */ public class Generators { public static<T> Collection<T> fill(Collection<T> coll,Generator<T> gen,int n) { System.out.println("gen.next():"+gen.next()); for(int i=0;i<n;i++) { coll.add(gen.next()); } return coll; } }
//BankTeller.java package org.rui.generics.anonymity; import java.util.ArrayList; import java.util.LinkedList; import java.util.List; import java.util.Queue; import java.util.Random; /** * 匿名内部类 内部类 就用于泛型 * generator 都生明成了static的,所以它们无法作为接口的一部分, * 由于无法用接口这样的特定的惯使用方法来泛化这二者。 * 虽然如此,它们fill()方法中都工作的非常好 * * @author lenovo * */ class Customer { private static long counter=1; private final long id=counter++; private Customer(){} public String toString(){return "Customer:"+id;} //每次会创建一个新的客户对象 public static Generator<Customer> generator(){ return new Generator<Customer>(){ public Customer next(){return new Customer();} }; } } //// 出纳员 class Teller { private static long counter=1; private final long id=counter++; private Teller(){} public String toString(){return "Teller"+id;} //Teller就仅仅创建了一个public 的generator对象 public static Generator<Teller> generator=new Generator<Teller>() { public Teller next() { return new Teller(); } }; } ////////////// 出纳员 public class BankTeller { public static void serve(Teller t,Customer c) { System.out.println(t+" serves "+c); } public static void main(String[] args) { Random random=new Random(47); //生成客户对象15个 Queue<Customer> line=new LinkedList<Customer>(); Generators.fill(line, Customer.generator(), 15); //出纳员对象4个 List<Teller> tellers=new ArrayList<Teller>(); Generators.fill(tellers, Teller.generator, 4); for(Customer c:line) serve(tellers.get(random.nextInt(tellers.size())),c); } } /*output: Teller3 serves Customer1 Teller2 serves Customer2 Teller3 serves Customer3 Teller1 serves Customer4 Teller1 serves Customer5 Teller3 serves Customer6 Teller1 serves Customer7 Teller2 serves Customer8 Teller3 serves Customer9 Teller3 serves Customer10 Teller2 serves Customer11 Teller4 serves Customer12 Teller2 serves Customer13 Teller1 serves Customer14 Teller1 serves Customer15 * *///:~~~
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