这是写给我自己和我这种初学者看的.
Java作为1个强面向对象语言, 基本上所有东西(成员和方法)都是写在class(类)里面的.
但是也存在一种与class平行的东西, 它就是interface , 中文译成接口. 本屌能力有限在这里这能写写Interface的一些语法规则与存在意义.
Java里的接口, 就是抽象方法和常量值的集合.
这里的定义相当表面, 就如java里的类是成员和方法的集合一样.
作为1个初学者, 可以简单理解为接口就是一种特殊的抽象类. 区别下面会详细提到.
[public] interace interface_name [extends <Superinterface_list>]{
//public static final members
.....................
//public abstract methods
.......
}
下面是1个简单的例子:
interface It_1{
int i = 10; //public static final
//int j; //error all the members in a interface must be a const member
//& need assignment
//public abstract It_1(); //error, must without a constructor
void print(); //public abstract
}上面就简单定义了一个接口It_1. 接下来讲下接口定义的一些关键点:
外部interface前面的修饰符有两种:
如果架上public 则通不过编译.
这种情况下, 这个接口只能被同1个包内的类访问. 其他类不能访问.
例如上面例子中的
int i = 10; 就相当于 public static final int i =10;
但是你写成
static final int i =10;
final int i = 10;
都是可以通过编译的, 但是i这个成员实际上还是 public static final的, 性质没变.
但是不能用protected 或 private 来修饰成员, 否则编译失败.
class It_class1 implements It_1{ //implement an interface
void f(){
//i = 10; error cannot do assignment for a const member
int j = this.i;
}
//void print(){ the signal of authority cannot smaller than super class‘s(interface)
public void print(){ // overwrite an the abstract method.
}
}
public class Interface_1{
public static void f(){
It_1 a = new It_class1(); // Poly
a.print();
}
}package Interface_kng.Extend;
interface Itf_1{
int i = 1;
void f();
}
interface Itf_3 extends Itf_1{
int j = 3;
}
class Itf_class1 implements Itf_3{
public void f(){ //overwrite
System.out.printf("i is %d, j is %d\n", this.i, this.j);
}
}
public class Interface_3{
public static void f(){
Itf_class1 a = new Itf_class1();
a.f();
}
}interface Itf_1{
int i = 1;
void f();
}
interface Itf_2{
int k = 2;
void g();
}
interface Itf_3 extends Itf_1, Itf_2{
int j = 3;
}
class Itf_class2 implements Itf_3{
public void f(){ //overwrite
System.out.printf("i is %d, k is %d, j is %d\n", this.i, this.k, this.j);
}
public void g(){
}
}
public class Interface_3{
public static void f(){
Itf_class2 a = new Itf_class2();
a.f();
}
}interface Itf_1{
int i = 1;
void f();
}
interface Itf_2{
String i = "abc";
int k = 2;
void g();
}
interface Itf_3 extends Itf_1, Itf_2{
int j = 3;
}
class Itf_class2 implements Itf_3{
public void f(){ //overwrite
System.out.printf("i1 is %d, i2 is %s, k is %d, j is %d\n", Itf_1.i, Itf_2.i, this.k, this.j);
}
public void g(){
}
}package Interface_kng.Extend;
interface Itf_1{
int i = 1;
void f();
}
interface Itf_2{
String i = "abc";
int k = 2; //same name with Itf_1
void f(); //same name with Itf_1
void g();
}
interface Itf_3 extends Itf_1, Itf_2{
int j = 3;
}
class Itf_class2 implements Itf_3{
public void f(){ //overwrite
System.out.printf("i1 is %d, i2 is %s, k is %d, j is %d\n", Itf_1.i, Itf_2.i, this.k, this.j);
}
public void g(){
}
}interface Itf_1{
int i = 1;
void f();
}
interface Itf_2{
String i = "abc";
int k = 2; //same name with Itf_1
int f(); //same name with Itf_1, but diff return type
void g();
}
interface Itf_1{
int i = 1;
void f();
}
interface Itf_2{
String i = "abc";
int k = 2; //same name with Itf_1
void f(); //same name with Itf_1
void g();
}
class Itf_class1 implements Itf_1, Itf_2{
public void f(){ //overwrite
System.out.printf("i1 is %d, i2 is %s, k is %d", Itf_1.i, Itf_2.i, this.k);
}
public void g(){
}
}
原文：http://blog.csdn.net/nvd11/article/details/18888415