Java設計模式是指在Java語言中使用的一些經典的、被廣泛認可的設計模式。這些模式在很多情況下被稱為設計模式的三大家族：創建型模式、結構型模式和行為型模式。

Android開發中，設計模式也是一個非常重要的概念。Android應用程序中，常常需要對各個組件進行設計，如Activity、Service、BroadcastReceiver、ContentProvider等。Android開發中有很多設計模式可以使用，如MVP、MVC、觀察者模式等。

下面將介紹一些常見的Java設計模式與Android的結合使用：

//單例模式
public class Singleton {
private static Singleton instance;
private Singleton() {}
public static Singleton getInstance() {
if (instance == null) {
instance = new Singleton();
}
return instance;
}
}
//建造者模式
public class Person {
private final String name; 
private final int age;
private final String gender; 
private Person(Builder builder) { 
this.name = builder.name; 
this.age = builder.age;
this.gender = builder.gender; 
}
public static class Builder {
private String name;
private int age;
private String gender;
public Builder(String name) { 
this.name = name; 
}
public Builder age(int age) { 
this.age = age;
return this; 
}
public Builder gender(String gender) { 
this.gender = gender;
return this; 
}
public Person build() { 
return new Person(this); 
}
}
}
//策略模式
public interface Strategy {
int calculate(int a, int b);
}
public class AddStrategy implements Strategy {
@Override
public int calculate(int a, int b) {
return a + b;
}
}
public class SubStrategy implements Strategy {
@Override
public int calculate(int a, int b) {
return a - b;
}
}
public class Operation {
private Strategy mStrategy;
public void setStrategy(Strategy strategy) {
mStrategy = strategy;
}
public int calculate(int a, int b) {
return mStrategy.calculate(a, b);
}
}
//觀察者模式
public interface Observer {
void onChanged(Object obj);
}
public interface Observable {
void registerObserver(Observer observer);
void unregisterObserver(Observer observer);
void notifyObservers(Object obj);
}
public class LoginManager implements Observable {
private ListmObservers = new ArrayList<>();
public void login(String username, String password) { 
// 登錄邏輯
notifyObservers(user);
}
@Override
public void registerObserver(Observer observer) {
mObservers.add(observer);
}
@Override
public void unregisterObserver(Observer observer) {
mObservers.remove(observer);
}
@Override
public void notifyObservers(Object obj) {
for (Observer observer : mObservers) {
observer.onChanged(obj);
}
}