java常见集合的循环输出方式.doc

常见集合的循环输出方式一、List集合的循环输出List objList = new ArrayList(); 1) for (int i=0; iobjList.size(); i+) / 循环输出集合中的每个对象 Object object = objList.get(i); System.out.println(object); 2) for (Object obj:objList) / 循环输出集合中的每个对象 System.out.println(object); 3) 将List集合转换为迭代器Iterator接口，并且循环输出 List list = new ArrayList(); list.add(cheng); list.add(zhang); Iterator it = list.iterator(); while (it.hasNext() String str = (String)it.next(); System.out.println(str); 4) 将List集合转换为Object类型的数组,循环输出 List list = new ArrayList(); list.add(cheng); list.add(zeng); list.add(zhang); Object obj = list.toArray(); for (int i=0; iobj.length; i+) String s = (String)obji; System.out.println(s); 二.循环输出Set 1) 将Set集合转换为迭代器Iterator接口，并且循环输出 Set set = new HashSet(); set.add(cheng); set.add(zeng); set.add(zhang); Iterator it = set.iterator(); while (it.hasNext() String str = (String)it.next(); System.out.println(str); 2) 将Set集合转换为Object类型的数组 Set set = new HashSet(); set.add(cheng); set.add(zeng); set.add(zhang); Object obj = set.toArray(); for (int i=0;iobj.length;i+) String s = (String)obji; System.out.println(s); 三.循环输出Map 1) 直接循环Map对象 Map map = new HashMap(); map.put(1,cheng); map.put(2,zeng); map.put(3,zhang); / 输出键值 for (String key:map.keySet() System.out.println(key); / 输出value for (String value:map.values() System.out.println(value); 2) Map map = new HashMap(); map.put(1,cheng); map.put(2,zeng); map.put(3,zhang); Iterator it = map.entrySet().iterator(); while (it.hasNext() Map.Entry