I am learning design patterns in Java from an online video tutorial. I have learned the builder design pattern and I'm trying to implement what it does, but for me its showing some errors. Help me to resolve them.

```java
public class Phone {

    private String model;
    private String os;
    private int ram;
    private double screensize;
    private int battery;

    public Phone(String model, String os, int ram, double screensize, int battery) {
        super();
        this.model = model;
        this.os = os;
        this.ram = ram;
        this.screensize = screensize;
        this.battery = battery;
    }

    @Override
    public String toString() {
        return "Phone [model=" + model + ", os=" + os + ", ram=" + ram + ", screensize=" + screensize + ", battery="
                + battery + "]";
    }           
}

public class Phonebuilder {

    private String model;
    private String os;
    private int ram;
    private double screensize;
    private int battery;

    public Phonebuilder setModel(String model) {
        this.model = model;
        return this;
    }
    public Phonebuilder setOs(String os) {
        this.os = os;
        return this;
    }
    public Phonebuilder setRam(int ram) {
        this.ram = ram;
        return this;
    }
    public Phonebuilder setScreensize(double screensize) {
        this.screensize = screensize;
        return this;
    }
    public Phonebuilder setBattery(int battery) {
        this.battery = battery;
        return this;
    }

    public Phone getphone () {
        return new Phone(model, os, ram, screensize, battery);
    }
}

public class Test {

    public static void main(String[] args) {
        //It showing error in the below line like type mismatch.

        Phone p = new Phonebuilder().setBattery(9000).setModel("M31").setOs("Android");
        System.out.println(p);
    }

}

```