Java thread question

gistfile1.txt

class A
{
    synchronized void m1()
    {
        System.out.println("In m1 A");
    }
    void m2()
    {
        System.out.println("In m2 A");
    }
}
 // There are two threads T1 and T2. 
 // T1 is accessing m1 method. Will T2 be able to access m2 method on the same instance at the same time?

gistfile2.txt

import java.util.HashSet;
 
public class Customer {
 
    String name;
    int age;
 
    Customer(String name,int age)
    {
        this.name=name;
        this.age=age;
    }
    public static void main(String[] args) {
 
        Customer c1= new Customer("John",20);
        Customer c2= new Customer("John",20);
 
        HashSet<Customer> customerSet=new HashSet<>();
        customerSet.add(c1);
        customerSet.add(c2);
        System.out.println(customerSet.size());
    }
 
    // getters and setters
}

gistfile3.txt

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map.Entry;
 
public class IterateMapMain {
 
    public static void main(String args[])
    {
        // HashMap with Country as key and capital as value
        HashMap<String,String> map=new HashMap<String,String>();
        map.put("India","Delhi");
        map.put("Japan","Tokyo");
        map.put("France","Paris");
        map.put("Malaysia","Kuala Lumpur");
 
        // Iterating java iterator
        System.out.println("Iterating java Iterator");
        Iterator<String> countryKeySetIterator=map.keySet().iterator();
        while(countryKeySetIterator.hasNext()){
            String countryKey=countryKeySetIterator.next();
            map.put("Indonesia", "Jakarta");
            System.out.println(countryKey);
 
        }
        System.out.println("-----------------------------");
    }
 
}