JAVA容器小结

JAVA中的容器提供了非常完善的方法来保存对象，你可以使用这些工具来解决大数据量的问题。下面是笔者在开发中用到过的一些容器总结如此。

1 ArrayList

使用ArrayList非常简单：创建一个实例，用add()插入对象，然后用get()访问这些对象，此时需要索引，就象数组一样，但是不需要方括号，ArrayList还有size()方法，从而可以知道ArrayList的大小，也可以避免因为越界而引发错误。另外，ArrayList长于随机访问元素，但是在List的中间插入和移处元素时较慢。下面是ArrayList的例子(来自thinking in java)：

/**//*
*@(#)AppleAndOrangesWithGenerics.java1.0May17,2008
*@author:Administrator
*Copyright2008CSSWEBMicrosystems,Inc.Allrightsreserved.
*CSSWEBROOMPROPRIETARY/CONFIDENTIAL.Useissubjecttolicenseterms.
*/
packageholding;

importjava.util.ArrayList;

publicclassAppleAndOrangesWithGenerics...{

publicstaticvoidmain(String[]args)...{
ArrayList<Apple>apples=newArrayList<Apple>();
for(inti=0;i<3;i++)...{
apples.add(newApple());
}

for(inti=0;i<apples.size();i++)
System.out.println(((Apple)apples.get(i)).id());

for(Applec:apples)
System.out.println(c.id()+"-");
}
}

/**//*
*@(#)ListFeatures.java1.0May17,2008
*@author:Administrator
*Copyright2008CSSWEBMicrosystems,Inc.Allrightsreserved.
*CSSWEBROOMPROPRIETARY/CONFIDENTIAL.Useissubjecttolicenseterms.
*/
packageholding;

importjava.util.ArrayList;
importjava.util.Arrays;
importjava.util.Collections;
importjava.util.List;
importjava.util.Random;

importtypeinfo.pets.*;

publicclassListFeatures...{

publicstaticvoidmain(String[]args)...{
Randomrand=newRandom(47);
List<Pet>pets=Pets.arrayList(7);
System.out.print("1:"+pets);
System.out.println();
Hamsterh=newHamster();
pets.add(h);
System.out.print("2:"+pets);
System.out.println();
System.out.print("3:"+pets.contains(h));
System.out.println();
pets.remove(h);
Petp=pets.get(2);
System.out.print("4:"+pets.indexOf(p));
System.out.println();
Petcymric=newCymric();
System.out.print("5:"+pets.indexOf(cymric));
System.out.println();
System.out.print("6:"+pets.remove(cymric));
System.out.println();
System.out.print("7:"+pets.remove(p));
System.out.println();
System.out.print("8:"+pets);
System.out.println();
pets.add(3,newMouse());
System.out.print("9:"+pets);
System.out.println();
List<Pet>sub=pets.subList(1,4);
System.out.print("sublist:"+sub);
System.out.println();
System.out.print("10:"+pets.containsAll(sub));
System.out.println();
Collections.sort(sub);
System.out.print("sortedsublist:"+sub);
System.out.println();
System.out.print("11:"+pets.containsAll(sub));
System.out.println();
Collections.shuffle(sub,rand);
System.out.print("shufflesublist:"+sub);
System.out.println();
System.out.print("12:"+pets.containsAll(sub));
System.out.println();
List<Pet>copy=newArrayList<Pet>(pets);
sub=Arrays.asList(pets.get(1),pets.get(4));
System.out.print("sub:"+sub);
System.out.println();
copy.retainAll(sub);
System.out.print("13:"+copy);
System.out.println();
copy=newArrayList<Pet>(pets);
copy.remove(2);
System.out.print("14:"+copy);
System.out.println();
copy.removeAll(sub);
System.out.print("15:"+copy);
System.out.println();
copy.set(1,newMouse());//Replaceanelement
System.out.print("16:"+copy);
System.out.println();
copy.addAll(2,sub);
System.out.print("17:"+copy);
System.out.println();
System.out.print("18:"+pets.isEmpty());
System.out.println();
pets.clear();
System.out.print("19:"+pets);
System.out.println();
System.out.print("20:"+pets.isEmpty());
System.out.println();
pets.addAll(Pets.arrayList(4));
System.out.print("21:"+pets);
System.out.println();
Object[]o=pets.toArray();
System.out.print("22:"+o[3]);
System.out.println();
Pet[]pa=pets.toArray(newPet[0]);
System.out.print("23:"+pa[3].id());
System.out.println();
}
}

运行结果:

1:[Rat,Manx,Cymric,Mutt,Pug,Cymric,Pug]
2:[Rat,Manx,Cymric,Mutt,Pug,Cymric,Pug,Hamster]
3:true
4:2
5:-1
6:false
7:true
8:[Rat,Manx,Mutt,Pug,Cymric,Pug]
9:[Rat,Manx,Mutt,Mouse,Pug,Cymric,Pug]
sublist:[Manx,Mutt,Mouse]
10:true
sortedsublist:[Manx,Mouse,Mutt]
11:true
shufflesublist:[Mouse,Manx,Mutt]
12:true
sub:[Mouse,Pug]
13:[Mouse,Pug]
14:[Rat,Mouse,Mutt,Pug,Cymric,Pug]
15:[Rat,Mutt,Cymric,Pug]
16:[Rat,Mouse,Cymric,Pug]
17:[Rat,Mouse,Mouse,Pug,Cymric,Pug]
18:false
19:[]
20:true
21:[Manx,Cymric,Rat,EgyptianMau]
22:EgyptianMau
23:14

2 LinkedList

LinkedList也像ArrayList一样实现了基本的List接口,但是它执行某些操作(比如插入、删除)时要比ArrayList更加的高效，但是在随机访问操作方面要逊色一些。此外，LinkedList还添加了可以使其用作栈、队列或双端队列的方法。下面是关于LinkedList使用的例子：

/**//*
*@(#)LinkedListFeatures.java1.0May18,2008
*@author:Administrator
*Copyright2008CSSWEBMicrosystems,Inc.Allrightsreserved.
*CSSWEBROOMPROPRIETARY/CONFIDENTIAL.Useissubjecttolicenseterms.
*/
packageholding;

importjava.util.LinkedList;
importstaticnet.mindview.util.Print.*;

importtypeinfo.pets.Hamster;
importtypeinfo.pets.Pet;
importtypeinfo.pets.Pets;
importtypeinfo.pets.Rat;

publicclassLinkedListFeatures...{

publicstaticvoidmain(String[]args)...{

LinkedList<Pet>pets=newLinkedList<Pet>(Pets.arrayList(5));
print(pets);
print("pets.getFirst():"+pets.getFirst());
print("pets.element():"+pets.element());
print("pets.peek():"+pets.peek());

print("pets.remove():"+pets.remove());
print("pets.removeFirst():"+pets.removeFirst());
print("pets.poll():"+pets.poll());
print(pets);

pets.addFirst(newRat());
print("AfteraddFirst():"+pets);
pets.offer(Pets.randomPet());
print("Afteroffer():"+pets);
pets.add(Pets.randomPet());

print("Afteradd():"+pets);
pets.addLast(newHamster());
print("AfteraddLast():"+pets);
print("pets.removeLast():"+pets.removeLast());
}
}

运行结果：

[Rat,Manx,Cymric,Mutt,Pug]
pets.getFirst():Rat
pets.element():Rat
pets.peek():Rat
pets.remove():Rat
pets.removeFirst():Manx
pets.poll():Cymric
[Mutt,Pug]
AfteraddFirst():[Rat,Mutt,Pug]
Afteroffer():[Rat,Mutt,Pug,Cymric]
Afteradd():[Rat,Mutt,Pug,Cymric,Pug]
AfteraddLast():[Rat,Mutt,Pug,Cymric,Pug,Hamster]
pets.removeLast():Hamster

List的排序和查询：List排序和查询所使用的方法与对象数组所使用的相应方法有相同的名字和语法，只是用Collections的static方法代替Arrays的方法而已。例子如下：

/**//*
*@(#)ListSortSearch.java1.0May18,2008
*@author:Administrator
*Copyright2008CSSWEBMicrosystems,Inc.Allrightsreserved.
*CSSWEBROOMPROPRIETARY/CONFIDENTIAL.Useissubjecttolicenseterms.
*/
packagecontainers;

importjava.util.ArrayList;
importjava.util.Collections;
importjava.util.List;
importjava.util.ListIterator;
importjava.util.Random;

importcontainers.Utilities;
importstaticnet.mindview.util.Print.*;

publicclassListSortSearch...{

publicstaticvoidmain(String[]args)...{
List<String>list=newArrayList<String>(Utilities.list);
list.addAll(Utilities.list);
print(list);
Collections.shuffle(list,newRandom(47));
print("shuffled:"+list);
ListIterator<String>it=list.listIterator(10);
while(it.hasNext())...{
it.next();
it.remove();
}
print("Trimmed:"+list);
Collections.sort(list);
print("sorted:"+list);
Stringkey=list.get(7);
intindex=Collections.binarySearch(list,key);
print("Locationof"+key+"is"+index+
",list.get("+index+")="+list.get(index));
Collections.sort(list,String.CASE_INSENSITIVE_ORDER);
print("Case-insensitivesorted:"+list);
key=list.get(7);
index=Collections.binarySearch(list,key,String.CASE_INSENSITIVE_ORDER);
print("Locationof"+key+"is"+index+
",list.get("+index+")="+list.get(index));
}
}