遍历数组
String[] arr = { "包青天", "白乾涛", "baiqiantao", "bqt", "0909082401", };
for (int i = 0; i < arr.length; i++) {//普通for
System.out.println("第" + (i + 1) + "个元素为：" + arr[i]);
}
for (String i : arr) {//增强for
System.out.println("元素为：" + i);
}
遍历List、Set
List<String> mList = new ArrayList<String>();
mList.add("包青天a");
mList.add("包青天c");
mList.add("包青天b");
System.out.println(mList); //[包青天a, 包青天c, 包青天b]
for (String string : mList) {//增强for
System.out.println("---" + string);
}
Iterator<String> it = mList.iterator();
while (it.hasNext()) {//迭代器
System.out.println(it.next());
}
//list特有的ListIterator，可以双向遍历
ListIterator<String> it2 = mList.listIterator();
while (it2.hasNext()) {//List迭代器
System.out.println("*******" + it2.next());//执行完后指针移到了最后，这有这样才能使用hasPrevious遍历
}
while (it2.hasPrevious()) {//List迭代器
System.out.println(it2.previous() + "*****");
}
遍历Map
Map<Integer, String> map = new HashMap<Integer, String>();
map.put(30, "zhagsan");
map.put(17, "李四");
map.put(2016, "包青天");
System.out.println(map);//{17=李四, 2016=包青天, 30=zhagsan}
for (Integer key : map.keySet()) {//增强for遍历key
String value = map.get(key);
System.out.println(key + "---" + value);
}
for (Map.Entry<Integer, String> k_v : map.entrySet()) {//增强for遍历键值对
System.out.println(k_v);//17=李四
}
Iterator<Integer> iterator = map.keySet().iterator();
while (iterator.hasNext()) {//健的Set集合的迭代器
Integer key = iterator.next();
String value = map.get(key);
System.out.println(key + ":" + value);
}
Iterator<Map.Entry<Integer, String>> iterator2 = map.entrySet().iterator();
while (iterator2.hasNext()) {//键值对的迭代器
System.out.println(iterator2.next());//17=李四
}
List嵌套Map
ArrayList<HashMap<String, String>> array = new ArrayList<HashMap<String, String>>();
HashMap<String, String> hm1 = new HashMap<String, String>();
hm1.put("周瑜", "小乔");
hm1.put("吕布", "貂蝉");
// 把元素添加到array里面
array.add(hm1);
HashMap<String, String> hm2 = new HashMap<String, String>();
hm2.put("郭靖", "黄蓉");
hm2.put("杨过", "小龙女");
// 把元素添加到array里面
array.add(hm2);
// 遍历
for (HashMap<String, String> hm : array) {
Set<String> set = hm.keySet();
for (String key : set) {
String value = hm.get(key);
System.out.println(key + "-" + value);
}
System.out.println("//**************************");
}
}
Map嵌套Map
HashMap<String, HashMap<String, Integer>> mMap = new HashMap<String, HashMap<String, Integer>>();
HashMap<String, Integer> jcMap = new HashMap<String, Integer>();
jcMap.put("陈玉楼", 20);
jcMap.put("高跃", 22);
mMap.put("基础班", jcMap);
HashMap<String, Integer> jyMap = new HashMap<String, Integer>();
jyMap.put("李杰", 21);
jyMap.put("曹石磊", 23);
mMap.put("就业班", jyMap);
//遍历集合
Set<String> mKeySet = mMap.keySet();
for (String mKey : mKeySet) {
System.out.println(mKey);
HashMap<String, Integer> mValue = mMap.get(mKey);
Set<String> mValueKeySet = mValue.keySet();
for (String mValueKey : mValueKeySet) {
Integer mValueValue = mValue.get(mValueKey);
System.out.println("\t" + mValueKey + "-" + mValueValue);
}
}
Map嵌套List
HashMap<String, ArrayList<String>> hashMap = new HashMap<String, ArrayList<String>>();
ArrayList<String> array1 = new ArrayList<String>();
array1.add("吕布");
array1.add("周瑜");
array1.add("包青天");
hashMap.put("三国演义人物", array1);
ArrayList<String> array2 = new ArrayList<String>();
array2.add("令狐冲");
array2.add("林平之");
array2.add("包青天");
hashMap.put("笑傲江湖人物", array2);
//遍历集合
Set<String> keySet = hashMap.keySet();
for (String key : keySet) {
System.out.println(key);
ArrayList<String> valueList = hashMap.get(key);
for (String string : valueList) {
System.out.println("\t" + string);
}
}
多层嵌套
HashMap<String, HashMap<String, ArrayList<Student>>> mMap = new HashMap<String, HashMap<String, ArrayList<Student>>>();
// 北京校区数据
HashMap<String, ArrayList<Student>> bjmMap = new HashMap<String, ArrayList<Student>>();
ArrayList<Student> array1 = new ArrayList<Student>();
Student s1 = new Student("林青霞", 27);
Student s2 = new Student("风清扬", 30);
array1.add(s1);
array1.add(s2);
ArrayList<Student> array2 = new ArrayList<Student>();
Student s3 = new Student("赵雅芝", 28);
Student s4 = new Student("武鑫", 29);
array2.add(s3);
array2.add(s4);
bjmMap.put("基础班", array1);
bjmMap.put("就业班", array2);
mMap.put("北京校区", bjmMap);
// 广州校区数据
HashMap<String, ArrayList<Student>> xamMap = new HashMap<String, ArrayList<Student>>();
ArrayList<Student> array3 = new ArrayList<Student>();
Student s5 = new Student("范冰冰", 27);
Student s6 = new Student("刘意", 30);
array3.add(s5);
array3.add(s6);
ArrayList<Student> array4 = new ArrayList<Student>();
Student s7 = new Student("李冰冰", 28);
Student s8 = new Student("张志豪", 29);
array4.add(s7);
array4.add(s8);
xamMap.put("基础班", array3);
xamMap.put("就业班", array4);
mMap.put("广州校区", xamMap);
// 遍历集合
Set<String> mMapSet = mMap.keySet();
for (String mMapKey : mMapSet) {
System.out.println(mMapKey);
HashMap<String, ArrayList<Student>> mMapValue = mMap.get(mMapKey);
Set<String> mMapValueSet = mMapValue.keySet();
for (String mMapValueKey : mMapValueSet) {
System.out.println("\t" + mMapValueKey);
ArrayList<Student> mMapValueValue = mMapValue.get(mMapValueKey);
for (Student s : mMapValueValue) {
System.out.println("\t\t" + s.getName() + "-" + s.getAge());
}
}
}
时间： 2024-10-14 12:45:40