我正在继承领域接受安卓训练 我想知道为什么从最终关键字定义名称和颜色变量 - 当我删除这个关键字时,没有任何用处。当我得到这个关键字时,没有错误或事故- 请告诉我使用决赛的原因是什么
主要活动.java
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView txtAnimal = (TextView) findViewById(R.id.txtAnimal);
TextView txtCat = (TextView) findViewById(R.id.txtCat);
Animal animal1 = new Animal("tiger", "orange", 60, 80);
Cat cat1 = new Cat("persian", "brown", 40, 25, 4, true);
txtAnimal.setText(animal1.toString());
txtCat.setText(cat1.toString());
}
动物.java
public class Animal extends Object{
private final String name;
private final String color;
private int amountOfSpeed;
private int amountOfPower;
public Animal(String name, String color, int amountOfSpeed, int amountOfPower){
// this. for same name
this.name = name;
this.color = color;
this.amountOfSpeed = amountOfSpeed;
this.amountOfPower = amountOfPower;
}
// we can use setter because variable (name-color) are defined final
public String getName(){
return name;
}
public String getColor(){
return color;
}
public void setAmountOfSpeed(int amountOfSpeed){
this.amountOfSpeed = amountOfSpeed;
}
public int getAmountOfSpeed(){
return amountOfSpeed;
}
public void setAmountOfPower(int amountOfPower){
this.amountOfPower = amountOfPower;
}
public int getAmountOfPower(){
return amountOfPower;
}
public int evaluateAnimalValue(){
int result = amountOfSpeed *amountOfPower;
return result;
}
@Override
public String toString() {
return String.format("%s: %s %s: %s %s: %d %s: %d",
"Name", name,
"Color", color,
"Speed", amountOfSpeed,
"Power", amountOfPower);
}
}
猫.java
private final int numberOfLegs;
private boolean canHuntOtherAnimal;
public Cat(String name, String color, int amountOfSpeed, int amountOfPower, int numberOfLegs, boolean canHuntOtherAnimal){
super(name, color, amountOfSpeed, amountOfPower);
this.numberOfLegs = numberOfLegs;
this.canHuntOtherAnimal = canHuntOtherAnimal;
}
public int getNumberOfLegs() {
return numberOfLegs;
}
public boolean getCanHuntOtherAnimal() {
return canHuntOtherAnimal;
}
public void setCanHuntOtherAnimal(boolean canHuntOtherAnimal) {
this.canHuntOtherAnimal = canHuntOtherAnimal;
}
@Override
public String toString() {
return super.toString() + String.format(" %s: %d %s: %b",
"Legs", numberOfLegs,
"Fight", canHuntOtherAnimal) + " Animal Value: " + evaluateAnimalValue();
}
}
变量的 final 关键字表示无法修改该值。变量必须设置一次,然后无法更改。
变量在声明时初始化:
private final String name = "Rover";
。或在构造函数中,就像您在上面的代码中所做的那样。
在上面的代码示例中,setName 方法不适用于最终名称。但是,您可以调用setAmountOfSpeed,因为amountOfSpeed不是最终的。
final 关键字通常用于表示常量:
public final float PI = 3.14159;
这是一篇关于最终关键字的其他用法的文章。
https://www.geeksforgeeks.org/final-keyword-java/