接口隔离原则
介绍
客户端不要依赖不需要的接口，即一个类对另一个类的依赖应该建立在最小的接口上。
案例引入
A类，通过接口1依赖B类，C类通过依赖接口1依赖D类，A类只会用到1-3方法，C类只会使用到1，4，5方法。
uml类图
代码实现
public class Segregation1 {
public static void main(String[] args) {
A a = new A();
a.dependency1(new B());
a.dependency2(new B());
a.dependency3(new B());
C c = new C();
c.dependency1(new D());
c.dependency4(new D());
c.dependency5(new D());
}
}
interface Interface1{
public void operation1();
public void operation2();
public void operation3();
public void operation4();
public void operation5();
}
class B implements Interface1{
@Override
public void operation1() {
System.out.println("B 类 operation1");
}
@Override
public void operation2() {
System.out.println("B 类 operation2");
}
@Override
public void operation3() {
System.out.println("B 类 operation3");
}
@Override
public void operation4() {
System.out.println("B 类 operation4");
}
@Override
public void operation5() {
System.out.println("B 类 operation5");
}
}
class D implements Interface1{
@Override
public void operation1() {
System.out.println("D 类 operation1");
}
@Override
public void operation2() {
System.out.println("D 类 operation2");
}
@Override
public void operation3() {
System.out.println("D 类 operation3");
}
@Override
public void operation4() {
System.out.println("D 类 operation4");
}
@Override
public void operation5() {
System.out.println("D 类 operation5");
}
}
class A{
public void dependency1(Interface1 i){
i.operation1();
}
public void dependency2(Interface1 i){
i.operation2();
}
public void dependency3(Interface1 i){
i.operation3();
}
}
class C{
public void dependency1(Interface1 i){
i.operation1();
}
public void dependency4(Interface1 i){
i.operation4();
}
public void dependency5(Interface1 i){
i.operation5();
}
}
案例分析
- 类A通过接口interface1依赖B，类C通过接口依赖D，因为接口interface1对于A类和C类来说，不是最小的接口，就会导致类B，类D去重写使用不到的方法
- 将接口interface1拆分成独立的接口，类A和C分别和其依赖的接口建立依赖关系。也就是采用接口隔离原则。
- 接口interface1出现的方法，也拆分成三个接口 如下图所示
案例改进
uml类图
public class Segregation2 {
public static void main(String[] args) {
A a = new A();
a.dependency1(new B());
a.dependency2(new B());
a.dependency3(new B());
C c = new C();
c.dependency1(new D());
c.dependency4(new D());
c.dependency5(new D());
}
}
interface Interface1 {
public void operation1();
}
interface Interface2{
public void operation2();
public void operation3();
}
interface Interface3{
public void operation4();
public void operation5();
}
class B implements Interface1,Interface2{
@Override
public void operation1() {
System.out.println("B 类 operation1");
}
@Override
public void operation2() {
System.out.println("B 类 operation2");
}
@Override
public void operation3() {
System.out.println("B 类 operation3");
}
}
class D implements Interface1,Interface3 {
@Override
public void operation1() {
System.out.println("D 类 operation1");
}
@Override
public void operation4() {
System.out.println("D 类 operation4");
}
@Override
public void operation5() {
System.out.println("D 类 operation5");
}
}
class A{
public void dependency1(Interface1 i){
i.operation1();
}
public void dependency2(Interface2 i){
i.operation2();
}
public void dependency3(Interface2 i){
i.operation3();
}
}
class C{
public void dependency1(Interface1 i){
i.operation1();
}
public void dependency4(Interface3 i){
i.operation4();
}
public void dependency5(Interface3 i){
i.operation5();
}
}
这样设计的uml类图，满足了案例A,B,C,D四类需要，也满足了接口隔离原则。
只是为了记录自己的学习历程，且本人水平有限，不对之处，请指正。
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文章来源: 博客园
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