Android设计模式之单例模式
一、实例：
public class Staff {
public void work() {
//干活
}
}
public class CEO extends Staff {
private static final CEO mCeo = new CEO();
private CEO() {
}
public static CEO getCeo() {
return mCeo;
}
@Override
public void work() {
//管理VP
}
}
public class Company {
private List<Staff> allStaffs = new ArrayList<>();
public void addStaff(Staff per) {
allStaffs.add(per);
}
public void showAllStaffs() {
for (Staff per : allStaffs) {
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Staff:" + per.toString());
}
}
}
测试：
public class TestSingleton extends InstrumentationTestCase {
public void testRun() {
Company cp = new Company();
Staff ceo1 = CEO.getCeo();
Staff ceo2 = CEO.getCeo();
cp.addStaff(ceo1);
cp.addStaff(ceo2);
Staff vp1 = new VP();
Staff vp2 = new VP();
Staff staff1 = new Staff();
Staff staff2 = new Staff();
Staff staff3 = new Staff();
cp.addStaff(vp1);
cp.addStaff(vp2);
cp.addStaff(staff1);
cp.addStaff(staff2);
cp.addStaff(staff3);
cp.showAllStaffs();
}
}
1.懒汉模式：
public class Singleton {
private static Singleton instance;
private Singleton() {
}
public static synchronized Singleton getInstance() {
if (instance == null) {
instance = new Singleton();
}
return instance;
}
}
2.DCL模式：
public class Singleton2 {
private static Singleton2 sInstance = null;
private Singleton2() {
}
public void doSomething() {
System.out.println("so sth.");
}
public static Singleton2 getInstance() {
if (sInstance == null) {
synchronized (Singleton2.class) {
if (sInstance == null) {
sInstance = new Singleton2();
}
}
}
return sInstance;
}
}
3.静态内部类模式：
public class Singleton3 {
private Singleton3() {
}
public static Singleton3 getInstance() {
return SingletonHolder.sInstance;
}
private static class SingletonHolder {
private static final Singleton3 sInstance = new Singleton3();
}
private Object readResolve() {
return SingletonHolder.sInstance;
}
}
4.枚举模式：
public enum SingletonEnum {
INSTANCE;
public void doSomething() {
System.out.println(">>>>>>>>>>>>>>>>do.sth");
}
}
5.容器实现单利模式：
public class SingletonManager {
private static Map<String, Object> objMap = new HashMap<>();
private SingletonManager() {
}
public static void registerService(String key, Object instance) {
if (!objMap.containsKey(key)) {
objMap.put(key, instance);
}
}
public static Object getService(String key) {
return objMap.get(key);
}
}