Program returning blinking Cursor - bubble-sort

Question

So im doing a sort Method using the bubble sort and compareTo method
Yet for some reason, when I run the program it compiles, does no errors whatsoever and shows a blinking cursor in the program (as if u are about to type something in; which u can, just when u press enter nothing happens) and this cursor keeps blinking.
What's wrong here ? (code based on teacher's instructions)
public static void sort(ArrayList al)
{
Person p,p1,p2;
String a1,a2;
boolean flag = true;
System.out.println("Database will be sorted acc to ID ");
System.out.println();
do
{
flag = false;
for (int i=0;i<al.size()-1;i++)
{
p = (Person)al.get(i);
a1=((Person)al.get(i)).personID;
a2=((Person)al.get(i+1)).personID;
if (a1.compareTo(a2) > 0){
p1= (Person)al.get(i);
p2 =(Person)al.get(i+1);
}
}
}
while (flag = true);
if (flag = false)
{
for (int i = 0; i < al.size(); i++)
{
p = (Person) al.get(i);
System.out.println("----------" + (i+1) + "-----------");
System.out.println("ID Number: "+ p.personID);
System.out.println("Name: "+ p.name);
System.out.println("Day of Birth: " +p.dayDOB);
System.out.println("Month of Birth: " +p.monthDOB);
System.out.println("Year of Birth: " +p.yearDOB);
System.out.println("Telephone Number: " +p.telNum);
System.out.println("");
}
}

Answer 1

The problem is in this loop:
do
{
....
}
while (flag = true);
You want to compare flag to true, i.e. flag == true, but instead you set flag to true with flag = true. Therefore, the loop will not exit, but instead run forever (or until you terminate the program).
You have the same problem in the following if statement.