编译 Java 类、'illegal start of type'和'<identifier> expected'错误

Question

正在练习与Java中的构造师一起工作，这是我试图编译的类：

import java.util.*;
import java.lang.*;
public class mob{
    public Map enemies = new HashMap<String, Point>();
    public Point pn = new Point(1, 1);
    enemies.put("Peon", pn);
    public Point gn = new Point(5, 2);
    enemies.put("Goblin", gn);
    public Point tl = new Point(25, 8);
    enemies.put("Troll", tl);
    public Point oc = new Point(13, 5);
    enemies.put("Orc", oc);
    public String name;
    public int hp;
    public int dmg;
    public mob(String type){
      name=type;
      hp=enemies.get(type).getX();
      dmg=enemies.get(type).getY();
    }
    public mob(){
      name="Peon";
      hp=enemies.get("Peon").getX();
      dmg=enemies.get("Peon").getY();
    }
    void setName(String name){
            this.name=name;
    }

    public static void main(String[] args) {
      Scanner scan = new Scanner(System.in());
      System.out.System.out.println("Enter mob type:");
      String type = scan.nextln();
      if(mob.containsKey(type)){
        mob mob1 = new mob(type);
      }
      else{
        mob mob1 = new mob();
        mob1.setName(type);
      }
      System.out.println("You just spawned a "+mob1.name+", it has "+mob1.hp+" hp and "+mob1.dmg+" dmg!");
    }
}

主要方法旨在从控制台中获取一些输入，并使用映射（"敌人"）或默认MOB根据输入而创建特定的MOB。但是，当我尝试在命令提示符中编译此命令时，我会在所有敌人中获取错误。put（）方法，即：

mob.java:7: error: <identifier> expected
    enemies.put("Peon", pn);
               ^
mob.java:7: error: illegal start of type
    enemies.put("Peon", pn);
               ^
mob.java:9: error: <identifier> expected
    enemies.put("Goblin", gn);
               ^

等。

研究了类似的问题，并试图解决问题（因此所有公开声明），但无法弄清楚这一点...

使用Java和Javac是V11.0.2

Answer 1

钻石在那里告诉编译器通用类。但是，语法应为：

 public Map<String,Point> enemies = new HashMap<>();

和默认的 the enemies.put("Peon", pn);命令必须发生在构造函数中。

Answer 2

java中的语句必须使用一种方法。看来您正在尝试使用enemies.put("Goblin", gn);之类的语句初始化字段，因此我建议您为每个字段创建一个初始化方法。您的代码将变成：

import java.util.*;
import java.lang.*;
public class mob{
    public Map enemies = initialiseEnemies();
    public Point pn = new Point(1, 1);
    public Point gn = new Point(5, 2);
    public Point tl = new Point(25, 8);
    public Point oc = new Point(13, 5);
    public String name;
    public int hp;
    public int dmg;
    public static Map initialiseEnemies() {
        // Build the Hashmap here and return it.
    }
    public mob(String type){
      name=type;
      hp=enemies.get(type).getX();
      dmg=enemies.get(type).getY();
    }
    public mob(){
      name="Peon";
      hp=enemies.get("Peon").getX();
      dmg=enemies.get("Peon").getY();
    }
    void setName(String name){
            this.name=name;
    }

    public static void main(String[] args) {
      Scanner scan = new Scanner(System.in());
      System.out.System.out.println("Enter mob type:");
      String type = scan.nextln();
      if(mob.containsKey(type)){
        mob mob1 = new mob(type);
      }
      else{
        mob mob1 = new mob();
        mob1.setName(type);
      }
      System.out.println("You just spawned a "+mob1.name+", it has "+mob1.hp+" hp and "+mob1.dmg+" dmg!");
    }
}