ArrayList、LinkedList、HashMap的遍历(转)

ArrayList、LinkedList、HashMap是Java中常用到的几种集合类型，遍历它们是时常遇到的情况。当然还有一些变态的时候，那就是在遍历的过程中动态增加或者删除其中的元素。

下面的例子就是可以实现动态遍历ArrayList、LinkedList、HashMap。

  1 import java.util.ArrayList;
  2 import java.util.HashMap;
  3 import java.util.Iterator;
  4 import java.util.LinkedList;
  5 import java.util.ListIterator;
  6 import java.util.Map;
  7 import java.util.Map.Entry;
  8 
  9 /**
 10  * @Description:
 11  * @author Scott
 12  * @date 2014年2月21日 下午8:33:40
 13  */
 14 public class TraversalTest {
 15 
 16     ArrayList<String> arrayList = new ArrayList<String>();
 17     LinkedList<String> linkedList = new LinkedList<String>();
 18     HashMap<String, String> map = new HashMap<String, String>();
 19 
 20     public TraversalTest() {
 21         arrayList.add("1");
 22         arrayList.add("2");
 23         arrayList.add("3");
 24         arrayList.add("4");
 25         arrayList.add("5");
 26 
 27         linkedList.add("1");
 28         linkedList.add("2");
 29         linkedList.add("3");
 30         linkedList.add("4");
 31         linkedList.add("5");
 32 
 33         map.put("1", "1");
 34         map.put("2", "2");
 35         map.put("3", "3");
 36         map.put("4", "4");
 37         map.put("5", "5");
 38         
 39         System.out.println("Data has init over ...");
 40     }
 41 
 42     /**
 43      * ForEach Traversal.
 44      * The Effective-Java recommended this traversal type.
 45      * */
 46     public void arrayListTraversalNormal1() {
 47         System.out.println("ArrayList ForEach Traversal.");
 48         for(String str : arrayList){
 49             System.out.println(str);
 50         }
 51     }
 52     
 53     /**
 54      * Iterator Traversal.
 55      * */
 56     public void arrayListTraversalNormal2() {
 57         System.out.println("ArrayList Iterator Traversal.");
 58         Iterator<String> itor = arrayList.iterator();
 59         while(itor.hasNext()){
 60             System.out.println(itor.next().toString());
 61         }
 62     }
 63 
 64     /**
 65      * ForEach Traversal.
 66      * The Effective-Java recommended this traversal type.
 67      * */
 68     public void linkedListTraversalNormal1() {
 69         System.out.println("LinkedList ForEach Traversal.");
 70         for(String str : linkedList){
 71             System.out.println(str);
 72         }
 73     }
 74 
 75     /**
 76      * Iterator Traversal.
 77      * */
 78     public void linkedListTraversalNormal2() {
 79         System.out.println("LinkedList Iterator Traversal.");
 80         Iterator<String> itor = linkedList.iterator();
 81         while(itor.hasNext()){
 82             System.out.println(itor.next().toString());
 83         }
 84     }
 85     
 86     public void mapTraversalNormal() {
 87         System.out.println("HashMap Iterator Traversal.");
 88         Iterator<Entry<String, String>> itor = map.entrySet().iterator();
 89         Entry<String, String> entry = null;
 90         String key = null;
 91         String value = null;
 92         
 93         while(itor.hasNext()){
 94             entry = itor.next();
 95             key = entry.getKey();
 96             value = entry.getValue();
 97             
 98             System.out.println("key is " + key + ", value is " + value);
 99         }
100     }
101     
102     /**
103      * While traversing the arrayList, add '33' behind the '3' element.
104      * */
105     public void arrayListTraversalDynamic1() {
106         ListIterator<String> itor = arrayList.listIterator();
107         String str = null;
108         
109         while (itor.hasNext()) {
110             str = itor.next().toString();
111             if(str.equals("3")){
112                 itor.add("33");
113                 break;
114             }
115         }
116     }
117     
118     /**
119      * While traversing the arrayList, remove the '3' element.
120      * */
121     public void arrayListTraversalDynamic2() {
122         ListIterator<String> itor = arrayList.listIterator();
123         String str = null;
124         
125         while (itor.hasNext()) {
126             str = itor.next().toString();
127             if(str.equals("3")){
128                 itor.remove();
129                 break;
130             }
131         }
132     }
133 
134     /**
135      * While traversing the linkedList, add '33' behind the '3' element.
136      * */
137     public void linkedListTraversalDynamic1() {
138         ListIterator<String> itor = linkedList.listIterator();
139         String str = null;
140         
141         while (itor.hasNext()) {
142             str = itor.next().toString();
143             if(str.equals("3")){
144                 itor.add("33");
145                 break;
146             }
147         }
148     }
149     
150     /**
151      * While traversing the linkedList, remove the '3' element.
152      * */
153     public void linkedListTraversalDynamic2() {
154         ListIterator<String> itor = linkedList.listIterator();
155         String str = null;
156         
157         while (itor.hasNext()) {
158             str = itor.next().toString();
159             if(str.equals("3")){
160                 itor.remove();
161                 break;
162             }
163         }
164     }
165 
166     /**
167      * While traversing the arrayList, add '33' when we get the '3' element.
168      * */
169     @SuppressWarnings("rawtypes")
170     public void mapTraversalDynamic1() {
171         LinkedList<Map.Entry<String, String>> tempList = new LinkedList<Map.Entry<String, String>>();
172         tempList.addAll(map.entrySet());
173         ListIterator<Map.Entry<String, String>> itor = tempList.listIterator();
174         Map.Entry entry = null;
175 
176         while (itor.hasNext()) {
177             entry = (Map.Entry) itor.next();
178             Object key = entry.getKey();
179 
180             if (key.toString().equals("3")) {
181                 map.put("33", "33");
182             }
183         }
184     }
185     
186     /**
187      * While traversing the hashMap, remove the '3' element.
188      * */
189     @SuppressWarnings("rawtypes")
190     public void mapTraversalDynamic2() {
191         LinkedList<Map.Entry<String, String>> tempList = new LinkedList<Map.Entry<String, String>>();
192         tempList.addAll(map.entrySet());
193         ListIterator<Map.Entry<String, String>> itor = tempList.listIterator();
194         Map.Entry entry = null;
195 
196         while (itor.hasNext()) {
197             entry = (Map.Entry) itor.next();
198             Object key = entry.getKey();
199 
200             if(key.toString().equals("3")){
201                 map.remove("3");
202                 break;
203             }
204         }
205     }
206 
207     public static void main(String[] args) {
208         TraversalTest test = new TraversalTest();
209         
210         test.arrayListTraversalNormal1();
211         test.arrayListTraversalNormal2();
212         
213         System.out.println("While traversing the arrayList, add '33' behind the '3' element. The result is:");
214         test.arrayListTraversalDynamic1();
215         test.arrayListTraversalNormal1();
216         
217         System.out.println("While traversing the arrayList, remove the '3' element. The result is:");
218         test.arrayListTraversalDynamic2();
219         test.arrayListTraversalNormal1();
220         
221         System.out.println("-----------------------------------");
222         
223         test.linkedListTraversalNormal1();
224         test.linkedListTraversalNormal2();
225         
226         System.out.println("While traversing the linkedList, add '33' behind the '3' element. The result is:");
227         test.linkedListTraversalDynamic1();
228         test.linkedListTraversalNormal1();
229         
230         System.out.println("While traversing the linkedList, remove the '3' element. The result is:");
231         test.linkedListTraversalDynamic2();
232         test.linkedListTraversalNormal1();
233         
234         System.out.println("-----------------------------------");
235         test.mapTraversalNormal();
236         
237         System.out.println("While traversing the hashMap, add '33' when we get the '3' element. The result is:");
238         test.mapTraversalDynamic1();
239         test.mapTraversalNormal();
240         
241         System.out.println("While traversing the hashMap, remove the '3' element. The result is:");
242         test.mapTraversalDynamic2();
243         test.mapTraversalNormal();
244     }
245 
246 }

代码是最好的说明，运行结果如下：

Data has init over ...
ArrayList ForEach Traversal.
1
2
3
4
5
ArrayList Iterator Traversal.
1
2
3
4
5
While traversing the arrayList, add '33' behind the '3' element. The result is:
ArrayList ForEach Traversal.
1
2
3
33
4
5
While traversing the arrayList, remove the '3' element. The result is:
ArrayList ForEach Traversal.
1
2
33
4
5
-----------------------------------
LinkedList ForEach Traversal.
1
2
3
4
5
LinkedList Iterator Traversal.
1
2
3
4
5
While traversing the linkedList, add '33' behind the '3' element. The result is:
LinkedList ForEach Traversal.
1
2
3
33
4
5
While traversing the linkedList, remove the '3' element. The result is:
LinkedList ForEach Traversal.
1
2
33
4
5
-----------------------------------
HashMap Iterator Traversal.
key is 3, value is 3
key is 2, value is 2
key is 1, value is 1
key is 5, value is 5
key is 4, value is 4
While traversing the hashMap, add '33' when we get the '3' element. The result is:
HashMap Iterator Traversal.
key is 3, value is 3
key is 2, value is 2
key is 1, value is 1
key is 5, value is 5
key is 4, value is 4
key is 33, value is 33
While traversing the hashMap, remove the '3' element. The result is:
HashMap Iterator Traversal.
key is 2, value is 2
key is 1, value is 1
key is 5, value is 5
key is 4, value is 4
key is 33, value is 33