当我需要更改对象的类型时，有没有一种优雅的方法来重新创建对象？

正如所评论的，听起来排名应该只是你班级的一个属性。Fighter

除非子类具有超出超类的其他数据或行为，否则不应使用继承。

下面是一个完整的示例类。我们定义为具有三个命名常量对象的枚举，即您的三个等级。我们有一个 getter 和一个 setter 方法，供您更改实例上的排名字段。Rank

package work.basil.example;

import java.util.Objects;

public final class Fighter
{
    // Member fields
    private String name;
    private Rank rank;

    enum Rank { JUNIOR, MEDIOR, SENIOR; }

    // Constructor
    public Fighter ( String name ,
                     Rank rank )
    {
        this.name = name;
        this.rank = rank;
    }

    // Accessors
    public String getName ( )
    {
        return name;
    }

    public void setName ( final String name )
    {
       this.name = name ;
    }

    public Rank getRank ( )
    {
        return rank;
    }

    public void setRank ( final Rank rank )
    {
        this.rank = rank;
    }

    // `Object` overrides.
    @Override
    public boolean equals ( Object obj )
    {
        if ( obj == this ) return true;
        if ( obj == null || obj.getClass ( ) != this.getClass ( ) ) return false;
        var that = ( Fighter ) obj;
        return Objects.equals ( this.name , that.name ) &&
                Objects.equals ( this.rank , that.rank );
    }

    @Override
    public int hashCode ( )
    {
        return Objects.hash ( name , rank );
    }

    @Override
    public String toString ( )
    {
        return "Fighter[" +
                "name=" + name + ", " +
                "rank=" + rank + ']';
    }
}

用法：

Fighter alice = new Fighter ( "Alice" , Fighter.Rank.MEDIOR ) ;
alice.setRank( Rank.SENIOR ) ;  // Alice earned a promotion.