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问题 I have a column in my database that is typed double and I want to read the value from it using a JDBC ResultSet, but it may be null. What is the best way of doing this? I can think of three options none of which seem very good. Option 1: Bad because exception handling verbose and smelly double d; try { d = rs.getDouble(1); // do something } catch(SQLException ex) { if(rs.wasNull()) { // do something else } else { throw ex; } } Option 2: Bad because two fetches s = rs.getString(1); // or

问题 I have a list of objects say car . I want to filter this list based on some parameter using Java 8. But if the parameter is null , it throws NullPointerException . How to filter out null values? Current code is as follows requiredCars = cars.stream().filter(c -> c.getName().startsWith("M")); This throws NullPointerException if getName() returns null . 回答1: In this particular example I think @Tagir is 100% correct get it into one filter and do the two checks. I wouldn't use Optional.ofNullable

问题 Postgres is the database Can I use a NULL value for a IN clause? example: SELECT * FROM tbl_name WHERE id_field IN ('value1', 'value2', 'value3', NULL) I want to limit to these four values. I have tried the above statement and it doesn't work, well it executes but doesn't add the records with NULL id_fields. I have also tried to add a OR condition but this just make the query run and run with no end in sight. SELECT * FROM tbl_name WHERE other_condition = bar AND another_condition = foo AND

问题 On sometime, BluetoothDevice.getName() return null. How can i fix it? remoteDeviceName maybe null in following code. And i need distinguish my device and other devices by remoteDeviceName. BluetoothAdapter.getDefaultAdapter().startLeScan(new LeScanCallback() { @Override public void onLeScan(final BluetoothDevice device, final int rssi, byte[] scanRecord) { String remoteDeviceName = device.getName(); Log.d("Scanning", "scan device " + remoteDeviceName); }); 回答1: Finally, i found out the

问题 This question was inspired by this answer. I've always been of the philosophy that the callee is never responsible when the caller does something stupid, like passing of invalid parameters. I have arrived at this conclusion for several reasons, but perhaps the most important one comes from this article: Everything not defined is undefined. If a function doesn't say in it's docs that it's valid to pass nullptr , then you damn well better not be passing nullptr to that function. I don't think

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Why does Oracle 9i treat an empty string as NULL? I have a table in Oracle 10g named TEMP_TABLE with only two columns - id and description just for the sake of demonstration. The column id is a sequence generated primary key of type NUMBER(35, 0) not null and the column DESCRIPTION is a type of VARCHAR2(4000) not null . The basic table structure in this case would look something like the following. +------------

问题 Using Swift 1.1 and Xcode 6.2. I have a UIStoryboard containing a singular, custom UIViewController subclass. On it, I have an @IBOutlet connection of type UIView from that controller to a UIView subclass on the storyboard. I also have similar outlets for subviews of that view. See figure A. But at run time, these properties are nil (Figure B). Even though I have assured I've connected the outlets in Interface Builder. Thoughts : Is it possible that because I am using a subclass of a subclass

问题 Using Swift 1.1 and Xcode 6.2. I have a UIStoryboard containing a singular, custom UIViewController subclass. On it, I have an @IBOutlet connection of type UIView from that controller to a UIView subclass on the storyboard. I also have similar outlets for subviews of that view. See figure A. But at run time, these properties are nil (Figure B). Even though I have assured I've connected the outlets in Interface Builder. Thoughts : Is it possible that because I am using a subclass of a subclass

问题 A web service returns a huge XML and I need to access deeply nested fields of it. For example: return wsObject.getFoo().getBar().getBaz().getInt() The problem is that getFoo() , getBar() , getBaz() may all return null . However, if I check for null in all cases, the code becomes very verbose and hard to read. Moreover, I may miss the checks for some of the fields. if (wsObject.getFoo() == null) return -1; if (wsObject.getFoo().getBar() == null) return -1; // maybe also do something with

问题 I have a general question about writing init methods in Objective-C. I see it everywhere (Apple's code, books, open source code, etc.) that an init method should check if self = [super init] is not nil before continuing with initialisation. The default Apple template for an init method is: - (id) init { self = [super init]; if (self != nil) { // your code here } return self; } Why? I mean when is init ever going to return nil? If I called init on NSObject and got nil back, then something must