问不能在另一个文件中使用Java类

EN

public class Guitar2
{
    private String serialNumber;

    public Guitar2(String serialNumber)
    {
        this.serialNumber = serialNumber;
    }

    public String getSerialNumber()
    {
        return serialNumber;
    }
}

import java.util.List;
import java.util.LinkedList;

public class Inv2
{
    private List guitars;

    public Inv2()
    {   
        guitars = new LinkedList();
    }

    public void addGuitar(String serialNumber)
    {
        Guitar2 guitar = new Guitar2(serialNumber);
        guitars.add(guitar);
    }
}

[machine]me @ directory $ javac Inventory.java 
Inventory.java:18: cannot find symbol
symbol  : class Guitar
location: class Inventory
        Guitar guitar = new Guitar();
        ^
Inventory.java:18: cannot find symbol
symbol  : class Guitar
location: class Inventory
        Guitar guitar = new Guitar();
                            ^
2 errors

[me]machine @ ricks $ javac Inv2.java 
Note: Inv2.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.