从 class 创建新的 object 时出现“找不到符号”错误？

Question

public class Monster{

public final String TOMBSTONE = "Here Lies a Dead monster";


private int health = 500;
private int attack = 20;
private int movement = 2;

public String name = "Big Monster";


public int getAttack()
{
    return attack;
}

public int getMovement()
{
    return movement;
}

public int getHealth()
{
    return health;
}

public Monster(int health, int attack, int movement)
{
    this.health = health;
    this.attack = attack;
    this.movement = movement;

}

public Monster()
{

}}


public class Frank {

public static void main(String[] args){

    Monster NewMonster = new Monster();

    NewMonster.name = "Frank";

    System.out.println(NewMonster.name + " has an attack value of " + NewMonster.getAttack());

}

}

When trying to create a new object from my Monster class I get this error:

Frank.java:5: error: cannot find symbol
            Monster NewMonster = new Monster();
            ^

symbol: class Monster location: class Frank

I am very new to Java so sorry if this is a simple/easy fix but everything I have researched does not give me a solution to this error.

Thanks in advance for any replies/feedback.

Answer 1

You are not allowed to have multiple public classes in one file in Java. Therefore you need to either remove a public modifier of one of your classes or put the main method in your public class. I did the latter, since it is not necessary to place the main method in a seperate class just to instantiate your object.

I have updated your code and it runs now

public class Monster{

    public static void main(String[] args) {

        Monster NewMonster = new Monster();

        NewMonster.name = "Frank";

        System.out.println(NewMonster.name + " has an attack value of 
        " + NewMonster.getAttack());
    }

    public final String TOMBSTONE = "Here Lies a Dead monster";


    private int health = 500;
    private int attack = 20;
    private int movement = 2;

    public String name = "Big Monster";


    public int getAttack() {
        return attack;
    }

    public int getMovement(){
        return movement;
    }

    public int getHealth(){
        return health;
    }

    public Monster(int health, int attack, int movement){
        this.health = health;
        this.attack = attack;
        this.movement = movement;
    }

    public Monster(){}
}

Answer 2

1 You have to define only one class a public which will be saved as per your java file name (.java)

2 object references will be always in lower case

class Monster {

public final String TOMBSTONE = "Here Lies a Dead monster";

private int health = 500;
private int attack = 20;
private int movement = 2;

public String name = "Big Monster";

public int getAttack() {
    return attack;
}

public int getMovement() {
    return movement;
}

public int getHealth() {
    return health;
}

public Monster(int health, int attack, int movement) {
    this.health = health;
    this.attack = attack;
    this.movement = movement;

}

public Monster() {

}

} // only Frank can be a public class in a single java file, or else create two different java classes and import. public class Frank {

public static void main(String[] args){

Monster newMonster = new Monster();

newMonster.name = "Frank";

System.out.println(newMonster.name + " has an attack value of " + newMonster.getAttack());

} }

Output: Frank has an attack value of 20