Output not working, receive an error

For some reason, whenever I input one of the set colours in my code, it gives me an error. Can anyone see what the problem is here

This is my app class:

import javax.swing.JOptionPane;
public class binCollectionAPP{
public static void main(String[] args){
    //Declare Variables
    int apartmentNum, flag;
    String collect, binColour;

    //Objects
    binCollection bin = new binCollection();

    //Inputs
    apartmentNum=Integer.parseInt(JOptionPane.showInputDialog("Enter your apartment number"));
    binColour=JOptionPane.showInputDialog("Enter the colour bin you are checking");



    //set
    bin.setApartNum(apartmentNum);
    bin.setBinColour(binColour);

    //compute
    bin.compute();

    //get
    collect=bin.getCollectDay();
    flag=bin.getFlag();

    //output
    if(flag == 1){
        JOptionPane.showMessageDialog(null,"Error, incorrect bin colour");
    }
    else if(flag == 2){
        JOptionPane.showMessageDialog(null,"Error, incorrect apartment number");
    }
    else{
        JOptionPane.showMessageDialog(null,"Your collection day is "+collect);
    }

}
}

And my instantiable class is:

public class binCollection{
//Declare Vars
private int apartmentNum, flag;
private String collect, binColour;

//Constructor
public binCollection(){
    apartmentNum = 0;
    flag = 0;
    collect = "";
    binColour = "";
}

//set methods
public void setApartNum(int apartmentNum){
    this.apartmentNum = apartmentNum;
}
public void setBinColour(String binColour){
    this.binColour = binColour;
}

//compute
public void compute(){
    if(apartmentNum % 2 == 0){
        if(binColour == "brown" || binColour == "Brown" ){
            collect = "Monday";
        }
        else if(binColour == "black"){
            collect = "Tuesday";
        }
        else if(binColour == "green"){
            collect = "Wednesday";
        }
        else{
            flag = 1;
        }
    }
    else if(apartmentNum % 2 == 1){
        if(binColour == "brown"){
            collect = "Tuesday";
        }
        else if(binColour == "black"){
            collect = "Wednesday";
        }
        else if(binColour == "green"){
            collect = "Thursday";
        }
        else{
            flag = 1;
        }
    }
    else{
        flag = 2;
    }
}

//get methods
public String getCollectDay(){
    return collect;
}
public int getFlag(){
    return flag;
}
}

Can anyone see where I am going wrong?