例题:标准化考试,考试题目相同,每个人的解答不同。
class TestPaper{
public void TextQuestion1() {
System.out.println("问题一");
System.out.println("答案:"+Answer1());
}
public void TextQuestion2() {
System.out.println("问题二");
System.out.println("答案:"+Answer2());
}
public void TextQuestion3() {
System.out.println("问题三");
System.out.println("答案:"+Answer3());
}
protected String Answer1() {
return"";
}
protected String Answer2() {
return"";
}
protected String Answer3() {
return"";
}
}
class TestPaperA extends TestPaper{
protected String Answer1() {
return "b";
}
protected String Answer2() {
return "c";
}
protected String Answer3() {
return "a";
}
}
class TestPaperB extends TestPaper{
protected String Answer1() {
return "c";
}
protected String Answer2() {
return "a";
}
protected String Answer3() {
return "a";
}
}
public class Main{
public static void main(String[] args){
System.out.println("学生甲的试卷:");
TestPaper studentA=new TestPaperA();
studentA.TextQuestion1();
studentA.TextQuestion2();
studentA.TextQuestion3();
System.out.println("学生乙的试卷:");
TestPaper studentB=new TestPaperB();
studentB.TextQuestion1();
studentB.TextQuestion2();
studentB.TextQuestion3();
}
}
模板方法模式
abstract class AbstractClass{
public abstract void PrimitiveOperation1();
public abstract void PrimitiveOperation2();
public void TemplateMethod() {
PrimitiveOperation1();
PrimitiveOperation2();
System.out.println("");
}
}
class ConcreteClassA extends AbstractClass{
public void PrimitiveOperation1() {
System.out.println("具体类A方法1实现");
}
public void PrimitiveOperation2() {
System.out.println("具体类A方法2实现");
}
}
class ConcreteClassB extends AbstractClass{
public void PrimitiveOperation1() {
System.out.println("具体类B方法1实现");
}
public void PrimitiveOperation2() {
System.out.println("具体类B方法2实现");
}
}
public class Main{
public static void main(String[] args){
AbstractClass c;
c=new ConcreteClassA();
c.TemplateMethod();
c=new ConcreteClassB();
c.TemplateMethod();
}
}
特点:通过把不变行为搬移到超类,去除子类中的重复代码来实现它的优势。
优点:实现代码复用。
缺点:算法骨架不容易升级(模板和子类是非常耦合的,如果要变更模扳中的算法骨架,会影响子类变化)
什么情况下使用模板方法呢?
当需要完成在某一细节层次一致的一个过程或一系列步骤,但其个别步骤在更详细的层次上的实现可能不同的时候,通常要考虑用模板方法模式解决。