*JAVA Program* I need help fixing the errors in the code.

//Driver Class:

public class Main{

public static void main(String[] args) {

SmartPhone phone = new SmartPhone ("Sample", "40GB");

System.out.println("Total Playtime:" + phone.totalPlayTime());

System.out.println("To String Method: ");

System.out.println("To String Method after deleteALLSongs Method Invoked: ");

phone.deleteAllSongs ();

System.out.println(phone.toString( ));

}//end class

}//end main

//SmartPhone Class:

public class SmartPhone {

private String brand;

private String capacity;

private SongUpgrade [ ] songLibrary;

public SmartPhone (String brand, String capacity) {

this.brand = brand;

this.capacity = capacity;

this.songLibrary = new SongUpgrade[4];

songLibrary[0] = new SongUpgrade ("Song 1", 90);

songLibrary[1] = new SongUpgrade ("Song 2", 60);

songLibrary[2] = new SongUpgrade ("Song 3", 70);

songLibrary[3] = new SongUpgrade ("Song 4", 85);

}// smartphone

public boolean totalPlayTime(){

int total = 0;

for (SongUpgrade song : songLibrary) {

total = total + song.getLengthInSeconds();

}//end for

static void deleteAllSongs() {

this.songLibrary [0] = null;

this.songLibrary [1] = null;

this.songLibrary [2] = null;

this.songLibrary [3] = null;

}//end deleteAllSongs

public String toString() {

SongUpgrade song1=this.songLibrary[0];

SongUpgrade song2=this.songLibrary[1];

SongUpgrade song3=this.songLibrary[2];

SongUpgrade song4=this.songLibrary[3];

return "SmartPhone " + " Brand= " + brand + '\'' +

", Memory Capacity In GB= " + capacity + '\'' +

", Song Library= " + '\'' +

"Song 1='" + song1.toString() + '\'' +

", Song 2= " + song2.toString() + '\'' +

", Song 3= " + song3.toString() + '\'' +

", Song 4= " + song4.toString() + '\'' +

'}';

}//end toString

public class SongUpgrade{

private String title;

private int lengthInSeconds;

public SongUpgrade(String title, int lengthInSeconds){

this.title = title;

this.lengthInSeconds = lengthInSeconds;

}

public int getLengthInSeconds(){

return this.lengthInSeconds;

}

public String toString() {

return "SongUpgrade " +

"title=''" + title + '\'' +

", lengthInSeconds='" + lengthInSeconds + '\'' +

'}';

}//end string

}//end class

}//end class

//SongUpgrade Class:

class SongUpgrade{

public int totalPlayTime() {

return 1;

}

public class SmartPhone {

private String brand;

private int capacity;

private SongUpgrade[ ] songLibrary;

//two-args constructor

public SmartPhone (String brand, int capacity) {

this.brand=brand;

this.capacity=capacity;

// add songs

//creates 4 different objects of SongUpgrade class.

SongUpgrade song1= new SongUpgrade();

SongUpgrade song2= new SongUpgrade();

SongUpgrade song3= new SongUpgrade();

SongUpgrade song4= new SongUpgrade();

// add these four objects into songLibrary array

songLibrary=new SongUpgrade [4];

songLibrary[0]= song1;

songLibrary[1]= song2;

songLibrary[2]= song3;

songLibrary[3]= song4;

}

// this is a method-- it will delete all songs from the songLibrary (line 24-28)

public void deleteAllSongs() {

//iterate over songLibrary

for (int i=0; i

// set songLibrary data to null.

songLibrary[i]= null;

}//end for

}//end deleteAllSongs

}

}