[英]how can i write a user input based constructor?
我想要多个类,并希望根据用户输入构造一个类。 具体来说,我正在编写文字冒险游戏,并为玩家可以使用的每种“玩家类别”提供了一个类别。 我的三个班级扩展了父级“统计”班级。
这是我的代码的一部分:(我使用打印构造函数来提高书写效率)
switch (answer) {
case 1:
{
adv.print("you are a mage");
mainCharacterMage mainCharacter = new mainCharacterMage();
break;
}
case 2:
{
adv.print("you are an assasin");
mainCharacterAssasin mainCharacter = new mainCharacterAssasin();
break;
}
case 3:
{
adv.print("you are a fighter");
mainCharacterFighter mainCharacter = new mainCharacterFighter();
break;
}
default:
adv.print("error wrong answer");
break;
}
String printThis = Integer.toString(mainCharacter.getHealth());
adv.print("your health is "+printThis);
我假设这三个子类的父类称为MainCharacter
。
首先, mainCharacter
必须为MainCharacter
类型,除非您愿意在每次要使用mainCharacter
时进行instanceof
检查和强制转换。 每一个动作,你需要做上mainCharacter
将需要加以界定MainCharacter
,而不是在子类。
其次,你需要声明mainCharacter
的外部switch
,然后在把它定义switch
:
MainCharacter mainCharacter; // Declare it outside
switch (answer) {
case 1:
{
adv.print("you are a mage");
mainCharacter = new MainCharacterMage(); // Then define it on the inside
break;
}
case 2:
{
adv.print("you are an assasin");
mainCharacter = new MainCharacterAssasin();
break;
}
case 3:
{
adv.print("you are a fighter");
mainCharacter = new MainCharacterFighter();
break;
}
default:
adv.print("error wrong answer");
break;
}
可能是这样的
public interface Character {
// here is all common method of your Character
}
public class CharacterFactory {
private class CharacterMage implements Character {
// here is implementation
}
private class CharacterAssasin implements Character {
// here is implementation
}
public Character createCharacter(String characterName) {
switch (characterName) {
case "Mage":
return new CharacterMage();
case "Assasin":
return new CharacterAssasin();
default:
throw new IllegalArgumentException("Incorrect character type " + characterName);
}
}
根据类之间的差异,可以仅使用一个MainCharacter class
以及每个类的不同工厂方法来完成此操作。
例如,像这样设置MainCharacter类:
public class MainCharacter{
public int health;
public int damage;
// etc.
public static MainCharacter buildMage(){
health = 5;
damage = 20;
// etc.
}
public static MainCharacter buildAssassin(){
health = 10;
damage = 10;
// etc.
}
public static MainCharacter buildMage(){
health = 20;
damage = 5;
// etc.
}
}
然后像这样创建MainCharacter:
switch (answer) {
case 1:
{
adv.print("you are a mage");
MainCharacter main_character = MainCharacter.buildMage();
break;
}
case 2:
{
adv.print("you are an assasin");
MainCharacter main_character = MainCharacter.buildAssassin();
break;
}
case 3:
{
adv.print("you are a fighter");
MainCharacter main_character = MainCharacter.buildFighter();
break;
}
注意:这减少了必须创建的类的数量,但是仅当类之间的差异只是不同的初始统计信息时才合适。 如果不同的类实际上具有本质上不同的方法,则需要继承。
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