迭代器为我们提供了统一的遍历容器的方式,参见以下示例代码:
迭代器遍历List:
public class Testl {
public static void main(String[] args) {
List<String> aList = new ArrayList<String>();
for (int i = 0; i < 5; i++) {
aList.add("a" + i);
}
System.out.println(aList);
for (Iterator<String> iter = aList.iterator(); iter.hasNext();) {
String temp = iter.next();
System.out.print(temp + "\t");
if (temp.endsWith("3")) {// 删除3结尾的字符串
iter.remove();
}
}
System.out.println();
System.out.println(aList);
}
}
执行结果如图所示:
注:
如果遇到遍历容器时,判断删除元素的情况,使用迭代器遍历!
迭代器遍历Set:
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class Tesths {
public static void main(String[] args) {
Set<String> set = new HashSet<String>();
for (int i = 0; i < 5; i++) {
set.add("a" + i);
}
System.out.println(set);
for (Iterator<String> iter = set.iterator(); iter.hasNext();) {
String temp = iter.next();
System.out.print(temp + "\t");
}
System.out.println();
System.out.println(set);
}
}
执行结果如图所示:
迭代器遍历Map一:
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
public class Testma {
public static void main(String[] args) {
Map<String, String> map = new HashMap<String, String>();
map.put("A", "张三");
map.put("B", "李四");
Set<Entry<String, String>> ss = map.entrySet();
for (Iterator<Entry<String, String>> iterator = ss.iterator(); iterator.hasNext();) {
Entry<String, String> e = iterator.next();
System.out.println(e.getKey() + "--" + e.getValue());
}
}
}
执行结果如图所示:
我们也可以通过map的keySet()、valueSet()获得key和value的集合,从而遍历它们。
迭代器遍历Map二:
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class Testhm {
public static void main(String[] args) {
Map<String, String> map = new HashMap<String, String>();
map.put("A", "张三");
map.put("B", "李四");
Set<String> ss = map.keySet();
for (Iterator<String> iterator = ss.iterator(); iterator.hasNext();) {
String key = iterator.next();
System.out.println(key + "--" + map.get(key));
}
}
}
执行结果如图所示:
遍历List方法一:普通for循环
for(int i=0;i<list.size();i++){//list为集合的对象名
String temp = (String)list.get(i);
System.out.println(temp);
}
遍历List方法二:增强for循环(使用泛型!)
for (String temp : list) {
System.out.println(temp);
}
遍历List方法三:使用Iterator迭代器(1)
for(Iterator iter= list.iterator();iter.hasNext();){
String temp = (String)iter.next();
System.out.println(temp);
}
遍历List方法四:使用Iterator迭代器(2)
Iterator iter =list.iterator();
while(iter.hasNext()){
Object obj = iter.next();
iter.remove();//如果要遍历时,删除集合中的元素,建议使用这种方式!
System.out.println(obj);
}
遍历Set方法一:增强for循环
for(String temp:set){
System.out.println(temp);
}
遍历Set方法二:使用Iterator迭代器
for(String temp:set){
System.out.println(temp);
}
遍历Map方法一:根据key获取value
Map<Integer, Man> maps = new HashMap<Integer, Man>();
Set<Integer> keySet = maps.keySet();
for(Integer id : keySet){
System.out.println(maps.get(id).name);
}
遍历Map方法二:使用entrySet
Set<Entry<Integer, Man>> ss = maps.entrySet();
for (Iterator iterator = ss.iterator(); iterator.hasNext();) {
Entry e = (Entry) iterator.next();
System.out.println(e.getKey()+"--"+e.getValue());