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。
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.Map;
import java.util.Map.Entry; /**
* @Description:
* @author Scott
* @date 2014年2月21日 下午8:33:40
*/
public class TraversalTest { ArrayList<String> arrayList = new ArrayList<String>();
LinkedList<String> linkedList = new LinkedList<String>();
HashMap<String, String> map = new HashMap<String, String>(); public TraversalTest() {
arrayList.add("1");
arrayList.add("2");
arrayList.add("3");
arrayList.add("4");
arrayList.add("5"); linkedList.add("1");
linkedList.add("2");
linkedList.add("3");
linkedList.add("4");
linkedList.add("5"); map.put("1", "1");
map.put("2", "2");
map.put("3", "3");
map.put("4", "4");
map.put("5", "5"); System.out.println("Data has init over ...");
} /**
* ForEach Traversal.
* The Effective-Java recommended this traversal type.
* */
public void arrayListTraversalNormal1() {
System.out.println("ArrayList ForEach Traversal.");
for(String str : arrayList){
System.out.println(str);
}
} /**
* Iterator Traversal.
* */
public void arrayListTraversalNormal2() {
System.out.println("ArrayList Iterator Traversal.");
Iterator<String> itor = arrayList.iterator();
while(itor.hasNext()){
System.out.println(itor.next().toString());
}
} /**
* ForEach Traversal.
* The Effective-Java recommended this traversal type.
* */
public void linkedListTraversalNormal1() {
System.out.println("LinkedList ForEach Traversal.");
for(String str : linkedList){
System.out.println(str);
}
} /**
* Iterator Traversal.
* */
public void linkedListTraversalNormal2() {
System.out.println("LinkedList Iterator Traversal.");
Iterator<String> itor = linkedList.iterator();
while(itor.hasNext()){
System.out.println(itor.next().toString());
}
} public void mapTraversalNormal() {
System.out.println("HashMap Iterator Traversal.");
Iterator<Entry<String, String>> itor = map.entrySet().iterator();
Entry<String, String> entry = null;
String key = null;
String value = null; while(itor.hasNext()){
entry = itor.next();
key = entry.getKey();
value = entry.getValue(); System.out.println("key is " + key + ", value is " + value);
}
} /**
* While traversing the arrayList, add '33' behind the '3' element.
* */
public void arrayListTraversalDynamic1() {
ListIterator<String> itor = arrayList.listIterator();
String str = null; while (itor.hasNext()) {
str = itor.next().toString();
if(str.equals("3")){
itor.add("33");
break;
}
}
} /**
* While traversing the arrayList, remove the '3' element.
* */
public void arrayListTraversalDynamic2() {
ListIterator<String> itor = arrayList.listIterator();
String str = null; while (itor.hasNext()) {
str = itor.next().toString();
if(str.equals("3")){
itor.remove();
break;
}
}
} /**
* While traversing the linkedList, add '33' behind the '3' element.
* */
public void linkedListTraversalDynamic1() {
ListIterator<String> itor = linkedList.listIterator();
String str = null; while (itor.hasNext()) {
str = itor.next().toString();
if(str.equals("3")){
itor.add("33");
break;
}
}
} /**
* While traversing the linkedList, remove the '3' element.
* */
public void linkedListTraversalDynamic2() {
ListIterator<String> itor = linkedList.listIterator();
String str = null; while (itor.hasNext()) {
str = itor.next().toString();
if(str.equals("3")){
itor.remove();
break;
}
}
} /**
* While traversing the arrayList, add '33' when we get the '3' element.
* */
@SuppressWarnings("rawtypes")
public void mapTraversalDynamic1() {
LinkedList<Map.Entry<String, String>> tempList = new LinkedList<Map.Entry<String, String>>();
tempList.addAll(map.entrySet());
ListIterator<Map.Entry<String, String>> itor = tempList.listIterator();
Map.Entry entry = null; while (itor.hasNext()) {
entry = (Map.Entry) itor.next();
Object key = entry.getKey(); if (key.toString().equals("3")) {
map.put("33", "33");
}
}
} /**
* While traversing the hashMap, remove the '3' element.
* */
@SuppressWarnings("rawtypes")
public void mapTraversalDynamic2() {
LinkedList<Map.Entry<String, String>> tempList = new LinkedList<Map.Entry<String, String>>();
tempList.addAll(map.entrySet());
ListIterator<Map.Entry<String, String>> itor = tempList.listIterator();
Map.Entry entry = null; while (itor.hasNext()) {
entry = (Map.Entry) itor.next();
Object key = entry.getKey(); if(key.toString().equals("3")){
map.remove("3");
break;
}
}
} public static void main(String[] args) {
TraversalTest test = new TraversalTest(); test.arrayListTraversalNormal1();
test.arrayListTraversalNormal2(); System.out.println("While traversing the arrayList, add '33' behind the '3' element. The result is:");
test.arrayListTraversalDynamic1();
test.arrayListTraversalNormal1(); System.out.println("While traversing the arrayList, remove the '3' element. The result is:");
test.arrayListTraversalDynamic2();
test.arrayListTraversalNormal1(); System.out.println("-----------------------------------"); test.linkedListTraversalNormal1();
test.linkedListTraversalNormal2(); System.out.println("While traversing the linkedList, add '33' behind the '3' element. The result is:");
test.linkedListTraversalDynamic1();
test.linkedListTraversalNormal1(); System.out.println("While traversing the linkedList, remove the '3' element. The result is:");
test.linkedListTraversalDynamic2();
test.linkedListTraversalNormal1(); System.out.println("-----------------------------------");
test.mapTraversalNormal(); System.out.println("While traversing the hashMap, add '33' when we get the '3' element. The result is:");
test.mapTraversalDynamic1();
test.mapTraversalNormal(); System.out.println("While traversing the hashMap, remove the '3' element. The result is:");
test.mapTraversalDynamic2();
test.mapTraversalNormal();
} }
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
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