1. Exception Classes In JAVA, except for the RunTimeException class, all exceptions must be caught or thrown.
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2. Class embedding
(1) A class can be embedded in another class, but not in an interface.
(2) In static method or other methods, can not directly create the inner class object, must be obtained by means.
There are two approaches:
class A {
class B {}
B getB() {
B b = new B();
return b;
}
}
static void m() {
A a = new A();
A.B ab = a.getB(); // or a.bab = a.new B();
}
(3) A class inherits an inner class of another class because superclasses are inner classes and the constructor of inner classes is not automatic
The constructor of the superclass needs to be explicitly called in the subclass constructor.
In cases of:
class C extends A.B {
C() {
new A().super(); // Call the inner class constructor.
}
}
The constructor can also be written like this:
C(A a) {
a.super();
} // Use this constructor to create an object, say C C = new C(a); A is the object of A.
(1) The interface is embedded in the class, can use the private modifier. At this point, the interface can only be implemented in the class it belongs to, other classes do not
Can access.
(2) The embedded interface must be public.
4. Multiple inheritance (1) a class inherits a class and an interface, so the class must be written first, the interface is written after, the interface between the use of a
No space.
(2) Multiple inheritance between interfaces. Note the use of the extends keyword.
(3) although a class only implements an interface, but not only to implement all the methods of the interface, but also to implement the interface
Methods of an inherited interface, all methods of which must be implemented in a class.
(1) All data in an interface is static and final, i.e., static constants. Although you can use these two keywords
, but the constant must be assigned an initial value.
(2) The methods in the interface are public. In the implementation interface class, the implementation method must be able to public keyword.
(3) If you use public to modify the interface, the interface must be the same as the file name.
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