數組的遍歷:四種方式
int[] arr = new int[] { 11, 2, 44, 1234 }; for (int i : arr) {//增強for循環 System.out.println(i); } System.out.println("*************************"); for (int i = 0; i < arr.length; i++) {//for循環遍歷 System.out.println(arr[i]); } System.out.println("*************************"); Integer[] arr3 = { 1, 23, 13, 1, 51, 542, 2 }; List<Integer> list2 = Arrays.asList(arr3);//數組轉集合然后迭代,但是注意類型不能為基本數據類型 Iterator iterator = list2.iterator(); while (iterator.hasNext()) { Object object = (Object) iterator.next(); System.out.println(object); } System.out.println("*************************"); String[] arr1 = { "ss", "sss", "xxxx" }; List<String> list = Arrays.asList(arr1); list.stream().forEach(x -> System.out.println(x));//java8新特性 stream
字符串遍歷:三種方式
String s = "xxx xxx x xxxxx xx x xxxx"; char[] arr2 = s.toCharArray();//字符串轉字符數組 for (char c : arr2) { System.out.println(c); } System.out.println("*************************"); for (int i = 0; i < arr2.length; i++) {//substring截取加for循環 System.out.println(s.substring(i, i + 1)); } System.out.println("*************************"); for (int i = 0; i < arr2.length; i++) { System.out.println(s.charAt(i));//charAt獲取每一位加for循環 }
集合的遍歷
public class Test12 { public static void main(String[] args) { // list的四種遍歷方式 List list = new ArrayList(); list.add("XXX"); list.add("FOR"); list.add("CASH"); Iterator iterator = list.iterator();// 迭代 while (iterator.hasNext()) { Object object = (Object) iterator.next(); System.out.println(object); } for (Object object : list) {// 增強for循環 System.out.println(object); } for (int i = 0; i < list.size(); i++) {// for循環 System.out.println(list.get(i)); } Object[] obj = list.toArray();// 集合轉數組,之后參考數組的遍歷方式 // Map的四種遍歷方式 Map<String, Integer> map = new HashMap<String, Integer>(); map.put("1", 4); map.put("2", 1); map.put("3", 9); Set key = map.keySet();// keySet獲取全部key Iterator iterator2 = key.iterator(); while (iterator2.hasNext()) { String object = (String) iterator2.next(); System.out.println(object + " " + map.get(object)); } for (Object object : key) {//增強for循環,遍歷key System.out.println(object + " " + map.get(object)); } Set<Entry<String, Integer>> entry = map.entrySet();// 獲取整個map對象 Iterator<Entry<String, Integer>> iterator3 = entry.iterator(); while (iterator3.hasNext()) { Map.Entry<String, Integer> entry2 = (Map.Entry<String, Integer>) iterator3.next(); System.out.println(entry2.getKey() + " " + entry2.getValue()); } for (Entry<String, Integer> entry2 : entry) {//增強for循環,遍歷entry對象 System.out.println(entry2.getKey() + " " + entry2.getValue()); } } }