Can anyone help me to solve these problem ?

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Java

This is my part of java project.Does anyone have any idea about my question that there are problems with delete lesson method in student class.It does not work correctly.Because when i want to delete lesson from listLesson ,the output is "No Exist!",but actually i have created a lesson object and added that lesson to listLesson.Really i dont know what is the problem.May be it is related with addlesson method,i think it does not add lesson to listLesson,so when i wan to delete it is output is" No Exist!".Please,if you have any idea about solving this problem,let me know.Thanks in advance :)

public class student {
    private String name;

    private int id;
    private lesson[]listLesson;
    private int size;
    private int number=0;
    
   
    public student(String name){
        this.name=name;
        listLesson = new lesson[size];
        this.size=5;
    }
    public boolean isExist(lesson l){
        for(int i=0; i < number; i++)
            if(listLesson[i].equals(l))
                if(listLesson[i].getNote()>=60)
                    return true;
        return false;
    }
    public void addLesson(lesson l){     
        if(!this.isExist(l)){
            if(number==size){
               lesson[] newList = new lesson[size+1];
               for(int i=0; i < size; i++){
                   newList[i]=listLesson[i];
               }
               listLesson=newList;
               size++;     
                // System.out.println(listLesson);
            }
            
            listLesson[number]= l;
            number++;
       }
    
        else
            System.out.println("Already passed :"+ l);
            
    }

    public student(String name, int id) {
        this.name = name;
        this.id = id;
    }
   
    public void deleteLesson(lesson l){
        int index=existList(l);
        if(index!=-1){
            lesson []newL=new lesson[size-1];
            for(int i=0;i<index;i++){
                newL[i]=listLesson[i];
            }
            for(int i=index+1;i<size-1;i++){
                newL[i]=listLesson[i+1];
             
            }
               listLesson=newL;
                size--;           
                
        }else{
            System.err.println("No Exist!");
        }
        
    }
    
        public int existList(lesson l){
        for(int i=0;i<number;i++){
            if(listLesson[i].equals(l.getCode())){
                return i;
            }
        }
        return -1;
    }

    public lesson[] getListLesson() {
        return listLesson;
    }





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

    public void setId(int id) {
        this.id = id;
    }

    public void setListLesson(lesson l) {
        this.listLesson=new lesson[size];
    }

    public String getName() {
        return name;
    }

    public int getId() {
        return id;
    }

    public boolean equals(student s) {
        if (this.id == s.id && this.name.equals(s.name)) {
            return true;
        }
        return false;
    }

 


    
   public String toString() {        
 String res="{";
  int i;
  for(i=0;i<size-1;i++){
      if(listLesson.length==0)
          res+="-, ";
      else
      res+=listLesson[i]+", ";
      
  }
  if(listLesson.length==0)
      res+="-";
  else
  res+=listLesson[i];
 
  return "student{" + "name=" + name + ", id=" + id + res+"}";
          }

};

What I have tried:

I have created some classes. But there are some problems.If someone can help me,please tell me.