关于java：我可以让某人验证我的SCJP考试的馆藏

Can I have someone verify my collections for the SCJP Exam

我一直在学习SCJP，现在是Oracle认证的专业JavaSE程序员考试。

我很难把自己的脑袋集中在所有不同的收藏品上，以及何时使用它们。我也喜欢闪存卡。所以我尝试创建一组基本上相同的类，除了它们使用的集合。我将必须确定输出将如何出来，以及每个集合的主要"特性"是什么。

不幸的是，我不相信自己。我想请人确认所有的信息都是准确的，如果有丢失的话。然后经过一些反馈/更正，我认为这将是一个伟大的练习，任何其他人试图了解Java集合。

所涵盖的集合包括：hashmap、hashtable、treemap、linkedhashmap、hashset、treeset、linkedhashset、arraylist、vector、linkedlist、priorityqueue。

我也把所有的文件分开，可以在这里下载：http://www.allgo.com/personal/mycollections.zip

提前谢谢

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import java.util.*;
import java.lang.*;
class MyItem implements Comparable{
private String name;
MyItem(String n){ name = n; }
public String toString(){return name;}
public String getName(){return name;}

public boolean equals(Object obj){
if(this==obj) return true;
else if(obj==null) return false;
else if(getName() != ((MyItem)obj).getName()) return false;
else return true;
}
public int hashCode(){ return 5; }
public int compareTo(MyItem b){return b.getName().compareTo(getName());}

}
public class MyCollections{
public static void main(String[] args){
MyHashMap.main(args); System.out.println("HashMap: Hash=Unsorted, Unordered. Map=key/value pair
##
");
MyHashtable.main(args); System.out.println("Hashtable: Thread Safe. Hash=Unsorted, Unordered. Map=key/value pair
##
");
MyTreeMap.main(args); System.out.println("TreeMap: Tree=sorted. Map=key/value.
##
");
MyLinkedHashMap.main(args); System.out.println("LinkedHashMap: Linked=Maintains Insertion Order. Hash=unsorted, unordered. Map=key/value pair.
##
");
MyHashSet.main(args); System.out.println("HashSet: Hash=Unsorted, Unordered. Set=Unique. Define=equals/hashCode
##
");
MyTreeSet.main(args); System.out.println("TreeSet: Tree=Sorted. Set=Unique. Define=Comparable/Comparator
##
");
MyLinkedHashSet.main(args); System.out.println("LinkedHashSet: Liniked=Maintains Insertion Order. Hash=Unsorted. Set=Unique. Define=equals/hashCode
##
");
MyArrayList.main(args); System.out.println("ArrayList: List=Queue. Maintains insertion order, Allowed duplicates
##
");
MyVector.main(args); System.out.println("Vector: Thread Safe. ArrayList. Maintains Insertion Order, Allows duplicates
##
");
MyLinkedList.main(args); System.out.println("LinkedList: Linked=Maintaines Insertion Order. List=Queue. Advanced ArrayList with more methods.
##
");
MyPriorityQueue.main(args); System.out.println("PriorityQueue: Define=Comparable/comparator
##
");
}
}
class MyHashMap{
public static void main(String[] args){
HashMap c = new HashMap();
MyItem Eight = new MyItem("Eight");
c.put(5, new MyItem("Five")); c.put(1, new MyItem("One")); c.put(8, Eight); c.put(3, new MyItem("Three"));
c.put(4, new MyItem("Four")); c.put(1, new MyItem("1")); c.put(8, Eight); c.put(9, new MyItem("Nine"));
c.remove(3); c.put(7, new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyHashtable{
public static void main(String[] args){
Hashtable c = new Hashtable();
MyItem Eight = new MyItem("Eight");
c.put(5, new MyItem("Five")); c.put(1, new MyItem("One")); c.put(8, Eight); c.put(3, new MyItem("Three"));
c.put(4, new MyItem("Four")); c.put(1, new MyItem("1")); c.put(8, Eight); c.put(9, new MyItem("Nine"));
c.remove(3); c.put(7, new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyTreeMap{
public static void main(String[] args){
TreeMap c = new TreeMap();
MyItem Eight = new MyItem("Eight");
c.put(5, new MyItem("Five")); c.put(1, new MyItem("One")); c.put(8, Eight); c.put(3, new MyItem("Three"));
c.put(4, new MyItem("Four")); c.put(1, new MyItem("1")); c.put(8, Eight); c.put(9, new MyItem("Nine"));
c.remove(3); c.put(7, new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyLinkedHashMap{
public static void main(String[] args){
LinkedHashMap c = new LinkedHashMap();
MyItem Eight = new MyItem("Eight");
c.put(5, new MyItem("Five")); c.put(1, new MyItem("One")); c.put(8, Eight); c.put(3, new MyItem("Three"));
c.put(4, new MyItem("Four")); c.put(1, new MyItem("1")); c.put(8, Eight); c.put(9, new MyItem("Nine"));
c.remove(3); c.put(7, new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyHashSet{
public static void main(String[] args){
HashSet c = new HashSet();
MyItem Eight = new MyItem("Eight");
c.add(new MyItem("Five")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Three"));
c.add(new MyItem("Four")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Nine"));
c.remove(3); c.add(new MyItem("Seven"));
System.out.println(c);//output?
}
}

class MyTreeSet{
public static void main(String[] args){
TreeSet c = new TreeSet();
MyItem Eight = new MyItem("Eight");
c.add(new MyItem("Five")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Three"));
c.add(new MyItem("Four")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Nine"));
c.remove(Eight); c.add(new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyLinkedHashSet{
public static void main(String[] args){
LinkedHashSet c = new LinkedHashSet();
MyItem Eight = new MyItem("Eight");
c.add(new MyItem("Five")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Three"));
c.add(new MyItem("Four")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Nine"));
c.remove(3); c.add(new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyArrayList{
public static void main(String[] args){
ArrayList c = new ArrayList();
MyItem Eight = new MyItem("Eight");
c.add(new MyItem("Five")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Three"));
c.add(new MyItem("Four")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Nine"));
c.remove(3); c.add(new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyVector{
public static void main(String[] args){
Vector c = new Vector();
MyItem Eight = new MyItem("Eight");
c.add(new MyItem("Five")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Three"));
c.add(new MyItem("Four")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Nine"));
c.remove(3); c.add(new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyLinkedList{
public static void main(String[] args){
LinkedList c = new LinkedList();
MyItem Eight = new MyItem("Eight");
c.add(new MyItem("Five")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Three"));
c.add(new MyItem("Four")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Nine"));
c.remove(3); c.add(new MyItem("Seven"));
System.out.println(c);//output?
}
}
class MyPriorityQueue{
public static void main(String[] args){
PriorityQueue c = new PriorityQueue();
MyItem Eight = new MyItem("Eight");
c.offer(new MyItem("Five")); c.offer(new MyItem("One")); c.offer(Eight); c.offer(new MyItem("Three"));
c.offer(new MyItem("Four")); c.offer(new MyItem("One")); c.offer(Eight); c.offer(new MyItem("Nine"));
System.out.println(c.peek());
System.out.println(c.poll());
c.offer(new MyItem("Seven"));
System.out.println(c);//output?
}
}

首先，您应该重构代码。基本上，无论你在哪里使用"复制粘贴"，都不要。

创建如下方法：

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private static void fill(Collection c) {
MyItem Eight = new MyItem("Eight");
c.add(new MyItem("Five")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Three"));
c.add(new MyItem("Four")); c.add(new MyItem("One")); c.add(Eight); c.add(new MyItem("Nine"));
c.remove(3); c.add(new MyItem("Seven"));
System.out.println(c);//output?
}

然后，不要使用现有的方法，而是执行以下操作：

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class MyVector{
public static void main(String[] args){
Vector c = new Vector();
fill(c);
}
}

对你所有的收藏品都这样做。

接下来，对地图执行类似的操作：

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private static void fill(Map<?,?> map) {
MyItem Eight = new MyItem("Eight");
map.put(5, new MyItem("Five")); map.put(1, new MyItem("One")); map.put(8, Eight); map.put(3, new MyItem("Three"));
map.put(4, new MyItem("Four")); map.put(1, new MyItem("1")); map.put(8, Eight); map.put(9, new MyItem("Nine"));
map.remove(3); map.put(7, new MyItem("Seven"));
System.out.println(map);//output?
}

您的代码将收缩，可读，甚至有一天会变得可用。