Nested switch structures are difficult to understand because you can easily confuse the when blocks of an inner
switch as belonging to an outer statement. Therefore nested switch statements should be avoided.
Specifically, you should structure your code to avoid the need for nested switch statements, but if you cannot, then consider moving
the inner switch to another function.
Noncompliant code example
public void foo(Integer i, Integer j) {
  switch on i {
    when 1 {System.debug(' 1'); }
    when 2 { System.debug(' 2'); }
    when -3 {
      switch on j {  // Noncompliant
        when 1 {System.debug(' 3');}
        when else {System.debug(' 4');}
      }
    }
  }
}
Compliant solution
public void foo(Integer i, Integer j) {
  switch on i {
    when 1 {System.debug(' 1'); }
    when 2 { System.debug(' 2'); }
    when -3 {bar(j);}
  }
}
public void bar(Integer j) {
  switch on j {
    when 1 {System.debug(' 3');}
    when else {System.debug(' 4');}
  }
}