How to implement the work of two cycles at the same time?

Question

Java

Hello, how to implement the work of two infinite loops at the same time?
For example, here:

int i = 0;
        int c = 1;
        int a = 0;
        int b = 1;
        while (i < c) {
            System.out.println("1");
        }
        while (a < b) {
            System.out.println("2");
        }

Only 1 is displayed, how to make them work at the same time?

Answer 1

Run them in two threads

Answer 2

Merge into one with two conditions