概念：
状态模式：Allow an object to alter its benhavior when its internal state changes. The object will appear to change its class. 当一个对象内在状态改变是允许改变行为，这个对象看起来像改变了其类型。
实现：
定义状态接口或抽象状态类
public abstract class AbstractCourse { public AbstractCourse(String teacherName) { this.teacherName = teacherName; } private String teacherName; public abstract void study(); public String getTeacherName() { return teacherName; } public void setTeacherName(String teacherName) { this.teacherName = teacherName; } }
状态具体实现
public class BiologyClass extends AbstractCourse { public BiologyClass(String teacherName) { super(teacherName); } @Override public void study() { System.out.println(this.getTeacherName() + "正在上生物课"); } }
public class MathClass extends AbstractCourse { public MathClass(String teacherName) { super(teacherName); } @Override public void study() { System.out.println(this.getTeacherName() + "正在上数学课"); } }
具体应用场景
public class School { private AbstractCourse math = new MathClass("数学老师"); private AbstractCourse biology = new BiologyClass("生物老师"); private AbstractCourse now; public void study(){ now.study(); } public AbstractCourse getMath() { return math; } public void setMath(AbstractCourse math) { this.math = math; } public AbstractCourse getBiology() { return biology; } public void setBiology(AbstractCourse biology) { this.biology = biology; } public AbstractCourse getNow() { return now; } public void setNow(AbstractCourse now) { this.now = now; } }
测试及结果：
public class StateTest { @Test public void statetest(){ School school = new School(); school.setNow(school.getMath()); school.study(); school.setNow(school.getBiology()); school.study(); } }
数学老师正在上数学课
生物老师正在上生物课
分析：
1.状态过多会导致子类过多。
2.封装性好，在不改变应用场景的情况下，实际上是改变了使用的不同类，但是对外外部而言是种改变了其中的属性（状态）。
原文：https://www.cnblogs.com/ben-mario/p/11134121.html