Map集合的两种遍历方式：Map集合无序
public class Map1 {
public static void main(String[] args) {
Map<String, String> map=new HashMap();
map.put("12", "ss");
map.put("13", "sz");
map.put("11", "tg");
map.put("90", "sp");
//遍历
Set<String> set=map.keySet();
for(String key:set) {
System.out.println(key+"------------"+map.get(key));
}
//遍历2
Set<Map.Entry<String, String>> set2=map.entrySet();
for(Map.Entry<String, String> sss:set2) {
System.out.println(sss.getKey()+"------"+sss.getValue());
}
}
}
LIst集合的增删查，有序
public class Demo7 {
public static void main(String[] args) {
//添加元素
ArrayList als=new ArrayList();
Student s1=new Student("12","XZG");
Student s2=new Student("15","fx");
Student s3=new Student("17","ff");
Student s4=new Student("23","oo");
Student s5=new Student("68","yy");
als.add(s1);
als.add(s2);
als.add(s3);
als.add(s4);
als.add(s5);
System.out.println("元素个数："+als.size());
System.out.println(als.toString());
//删除元素
als.remove(0);
System.out.println("元素个数"+als.size());
//遍历元素
Iterator it= als.iterator();
while(it.hasNext()) {
Student st=(Student)it.next();
System.out.println(st.toString());
}
ListIterator lit=als.listIterator();
while(lit.hasNext()) {
Student st=(Student)lit.next();
System.out.println(st.toString());
}
System.out.println(als.contains(s2));//判断此元素是否存在
System.out.println(als.isEmpty());//判断集合是否为空
}
}