JAVA interface inheritance and collections

review

20190701

Interface supplement

A, java is to achieve more than single inheritance

Single inheritance:

A class can have only one parent

public class D extends D1 {

}

2. Multi-realization

A class can implement multiple interfaces simultaneously
When a class implements multiple interfaces, which need to implement all the abstract methods declared in the interface of these

package day;

public class Demo1 {
public interface A {
void fun1();
}
public interface B {
void fun2();
}
public class AAA implements A,B{
@Override
public void fun1() {

}
@Override
public void fun2() {
}
}
}

3. The interfaces between each other can be inherited:

- public interface A{
  void fun1();
  }
  public interface B extends A{ //接口B继承自接口A
  void fun2();
  }
  public class AB implements B{
  @Override
  public void fun1() {
  }
  @Override
  public void fun2() {
  }
  }
  }

Set (key, about 50%) 4. java in

5. Collection

A so-called order-disorder means: if the order of the elements in the order taken into identical, orderly, that is inconsistent disordered

List: list where it is ordered elements, elements allow repeat

ArrayList: variable length arrays

Example:

public static void main(String[] args) {
  List list = new ArrayList)_;
  list.add("aa");
  list.add(123);
  list.add(true);
  list.add(new Date());
  list.add(124);
  list.add(3.14);

  System.out.println(list.get(0) + " ....    " + list.get(3));
  System.out.println(list.size());
  System.out.println(list);
  System.out.println(list.toString());

  for (Object obj : list) {
   System.out.println(obj);
  }

  list.remove(0);//根据下标移除

  list.clear();
  System.out.println(list.size());
}
}

6. Generics

public static void main(String[] args) {
  List<String> list = new ArrayList<>();
  list.add("1234");
  list.add("true");
  list.add("aaaa");
  list.add("bbbb");
  list.add("cccc");  String e3 = list.get(3);  System.out.println(e3);  int size = list.size();  System.out.println(size);  for (String item : list) {   System.out.println(item);  }  System.out.println("---------------------");  //Iterator迭代器  Iterator<String> iterator = list.iterator();  while (iterator.hasNext()) {//判断是否还有下一个元素，有的话返回true   String next = iterator.next();// remove the element, while the pointer to the current position   }   System.out.println (Next);








}
}

JAVA interface inheritance and collections

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