JAVA List、Map集合遍历
List集合遍历三种方式No.1 for(exp;exp;exp)No.2 for(\ val : List)No.3 Iterator Map集合遍历四种方式No.1 for循环中使用entryNo.2 for循环中使用map.KeySet() & map.values()No.3 IteratorNo.4 通过键找值遍历，这种方式的效率比较低，因为本身从键取值是耗时的操作；List集合遍历三种方式
No.1 for(exp;exp;exp)
ArrayList<String> list = new ArrayList<News>();list.add("a");list.add("b");list.add("c");for (int i = 0; i < list.size(); i++) {System.out.println(list.get(i));}
No.2 for(<T> val : List)
ArrayList<String> list = new ArrayList<News>();list.add("a");list.add("b");list.add("c");for (String str: list) {System.out.println(str);}
No.3 Iterator
ArrayList<String> list = new ArrayList<News>();list.add("a");list.add("b");list.add("c");Iterator<String> iter = list.iterator();while(iter.hasNext()){String str = iter.next();System.out.println(str)}
Map集合遍历四种方式
No.1 for循环中使用entry
Map<String,String> map = new HashMap<String,String>();map.put("Monday","星期一");map.put("Tuesday","星期二");for(Map.Entry<String,String> entry : map.entrySet()){String mapKey = entry.getkey();String mapValue = entry.getValue();System.out.println(mapKey + ":" + mapValue)}
No.2 for循环中使用map.KeySet() & map.values()
Map<String,String> map = new HashMap<String,String>();map.put("Monday","星期一");map.put("Tuesday","星期二");for(String key : map.KeySet()){System.out.println(key);}for(String vaule : map.values()){System.out.println(valeus);}
No.3 Iterator
Map<String,String> map = new HashMap<String,String>();map.put("Monday","星期一");map.put("Tuesday","星期二");Iterator<Entry<String,Stirng>> entries = map.entrySet().iterator();while(entries.hasNext()){Entry<String,Stirng> entry = entry.next();String key = entry.getKey();Stirng value = entry.getValue();System.out.println(key + ":" + value);}
No.4 通过键找值遍历，这种方式的效率比较低，因为本身从键取值是耗时的操作；
Map<String,String> map = new HashMap<String,String>();map.put("Monday","星期一");map.put("Tuesday","星期二");for(String key : map.KeySet()){String value = map.get(key);System.out.println(key + ":" + value);}
