Intellij says that this can be a Null-Pointer. But according javadoc-CodePudding

  private boolean checkStatusAct(Contract contract) {
        if (contract.getActs() == null || contract.getActs().isEmpty()) {
            return true;
        } else if (contract.getActs() != null || (!contract.getActs().isEmpty())) { //here
            for (ContractAct contractAct : contract.getActs()) {
                if (contractAct.getStatusId() == 15) { 
                    return true;
                }
            }
        }
        return false;
    }

Isn't it successively checked one by one and if it's not null (!= null || .isEmpty()) it never produces a NullPoi

CodePudding user response：

In Jav 8 or higher version. Assuming contract.getActs() is a list. You don't need to write else: You can do like

private boolean checkStatusAct(Contract contract) {
    if (contract.getActs() == null || contract.getActs().isEmpty()) {
        return true;
    }
    return contract.getActs().stream().anyMatch(c -> c.getStatusId() == 15);
}

CodePudding user response：

The problem is that

contract.getActs() != null || (!contract.getActs().isEmpty())

will throw a NullPointerException if contract.getActs() returns null. In that case contract.getActs() != null is false and because of the || operator the JVM must evaluate contract.getActs().isEmpty() which will throw the NullPointerException.

To correct this you should write

contract.getActs() != null && (!contract.getActs().isEmpty())

But this is effectively not needed, because your first if condition already handles the cases where contract.getActs() or contract.getActs().isEmpty(). It would be better to rewrite your code as

    private boolean checkStatusAct(Contract contract) {
        if (contract.getActs() == null || contract.getActs().isEmpty()) {
            return true;
        } else {
            for (ContractAct contractAct : contract.getActs()) {
                if (contractAct.getStatusId() == 15) { 
                    return true;
                }
            }
        }
        return false;
    }

Starting from Java 8 you can also use streams (navnath's solution).