Help for Tim.

//**Make sure your array list is declared near the top of the file.**
//**Don't copy and paste this code into yours, write it yourself.**

// Add button Code


 private void addActionPerformed(java.awt.event.ActionEvent evt) {

        marks.add(Integer.parseInt(gradeInput.getText()));

        gradesText.setText(gradesText.getText()+gradeInput.getText()+"\n");

    }


//Sort Button code

 private void SortActionPerformed(java.awt.event.ActionEvent evt) {

        Collections.sort(marks); //sort the arrarList

        gradesText.setText(""); //clear the text area

        for(int i=0;i<marks.size();i++){

            gradesText.setText(gradesText.getText() + marks.get(i) + "\n" ); //display the sorted list

        }
    }

//Analyze button code

private void AnalyseActionPerformed(java.awt.event.ActionEvent evt) {

        int[] levels=levels();

        analyseText.setText("Average: "+Float.toString(average())+"%\n\n");

        analyseText.setText(analyseText.getText()+"Maximum Grade: "+Integer.toString(maximum())+"%\n\n");

        analyseText.setText(analyseText.getText()+"Minimum Grade: "+Integer.toString(minimum())+"%\n\n");

        analyseText.setText(analyseText.getText()+"Range: "+Integer.toString(maximum()-minimum())+"%\n\n");

        analyseText.setText(analyseText.getText()+"Level 4: "+Integer.toString(levels[4])+"\n");

        analyseText.setText(analyseText.getText()+"Level 3: "+Integer.toString(levels[3])+"\n");

        analyseText.setText(analyseText.getText()+"Level 2: "+Integer.toString(levels[2])+"\n");

        analyseText.setText(analyseText.getText()+"Level 1: "+Integer.toString(levels[1])+"\n");

        analyseText.setText(analyseText.getText()+"R: "+Integer.toString(levels[0])+"\n");




    }

//AVERAGE
public float average(){

        float sum=0;
        float average;
        for (int i=0;i<marks.size();i++){
            sum+=marks.get(i);
        }
        average=sum/marks.size();

        return(average);
    }


//MAXIMUM

    public int maximum(){
        Collections.sort(marks);

        return marks.get(marks.size()-1);
    }

//Minimum

    public int minimum(){
        Collections.sort(marks);

        return marks.get(0);

    }


//Calculate levels

public int[] levels(){
        int[] levels = {0,0,0,0,0};

        Collections.sort(marks);

        for(int i=0;i<marks.size();i++){

            if(marks.get(i)<50)
                levels[0]++;
            else if(marks.get(i)>=50 && marks.get(i)<60)
                levels[1]++;
            else if(marks.get(i)>=60 && marks.get(i)<70)
                levels[2]++;
            else if(marks.get(i)>=70 && marks.get(i)<80)
                levels[3]++;
            else if(marks.get(i)>=80)
                levels[4]++;
        }

        return levels;
    }