This code is used in apex heap size error resolution tutorial of SFDC Stop

apex-heap-size-demo.cls

List<Account> accounts = new List<Account>();
for(Integer i=1; i<=10000; i++) {
    accounts.add(new Account(Name = 'Account ' + i));
}
insert accounts;

List<Account> accounts = [SELECT Id FROM Account];
System.debug('Heap size when queried list of accounts = ' + Limits.getHeapSize());

for(List<Account> accounts : [SELECT Id FROM Account]) {
    System.debug(Limits.getHeapSize());
}
System.debug('Max heap size after an SOQL for loop = ' + Limits.getHeapSize());

void callMe()
{
    List<Account> accounts = [SELECT Id FROM Account];
    System.debug(Limits.getHeapSize());
}
callme();
System.debug(Limits.getHeapSize());

List<Account> accounts = [SELECT Id FROM Account];
System.debug('Heap size when queried list of accounts = ' + Limits.getHeapSize());
accounts = null;
System.debug('Heap size when list is null = ' + Limits.getHeapSize());

List<Account> accounts = [SELECT Id FROM Account];
System.debug('Heap size when queried list of accounts = ' + Limits.getHeapSize());
accounts.clear();
System.debug('Heap size when list is cleared = ' + Limits.getHeapSize());