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Why don't I get a NullPointerException in Groovy in this case?

由 自作多情 提交于 2020-01-11 04:27:05
问题 I have this test code: def test = null test.each { } Why don't I get any exception? 回答1: The implementation of each tries to call the iterator method of it's target in a null-safe fashion . If each is called on a null object, or an object without an iterator method, nothing happens. I haven't seen the source code, but it could look something like this§ Object each(Closure closure) { if (this?.respondsTo("iterator")) { def iterator = this.iterator() while (iterator.hasNext() { def item =

Lambda表达式转换为sql

由 ≡放荡痞女 提交于 2020-01-11 03:43:24
/// <summary> /// 表达式转sql帮助类 /// </summary> public static class LambdaToSqlHelper { /// <summary> /// 从表达式获取sql /// </summary> /// <typeparam name="T"></typeparam> /// <param name="func"></param> /// <returns></returns> public static string GetSqlFromExpression<T>(Expression<Func<T, bool>> func) { if (func != null && func.Body is BinaryExpression be) { return BinarExpressionProvider(be.Left, be.Right, be.NodeType); } else { return " ( 1 = 1 ) "; } } /// <summary> /// 拆分、拼接sql /// </summary> /// <param name="left"></param> /// <param name="right"></param> /// <param name="type"></param> ///

What is the PHP syntax to check “is not null” or an empty string? [duplicate]

由 限于喜欢 提交于 2020-01-10 06:52:29
问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Check if a variable is empty Simple PHP question: I have this stement: if (isset($_POST["password"]) && ($_POST["password"]=="$password")) { ...//IF PASSWORD IS CORRECT STUFF WILL HAPPEN HERE } Somewhere above this statement I use the following line in my JavaScript to set the username as a variable both in my JavaScript and in my PHP: uservariable = <?php $user = $_POST['user']; print ("\"" . $user . "\"")?>;

How do I use SplashScreen without throwing a NullPointerException?

由 淺唱寂寞╮ 提交于 2020-01-10 06:07:07
问题 No matter what I try, SplashScreen.getSplashScreen() is always null . From searching online I see that this is a common issue, and that it has something to do with not giving the SplashScreen an image to use... Therefore, in navigating the methods it seemed to me that setImageURL(URL) should be used. This is still not working. There are similar questions on SO, such as this, which are not helpful and seem to suggest using a myriad of plugins or creating such a class from scratch extending

自学书籍.MySQL必知必会

由 余生颓废 提交于 2020-01-09 18:25:03
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 聚合函数: AVG([DISTINCT] expr) 1.返回某列的平均值,忽略列值为NULL的行 SELECT AVG(prod_price) AS avg_price FROM products WHERE vend_id = 1003; COUNT(expr) 1.返回某列的行数,COUNT(*)包含NULL空值行,COUNT(column)对特定列中具有值进行计数,忽略NULL值 SELECT COUNT(*) AS cust_num FROM customers; SELECT COUNT(cust_email) AS cust_num FROM customers; MAX([DISTINCT] expr) 1.返回某列的最大值,忽略列值为NULL的行 SELECT MAX(prod_price) AS max_price FROM products; MIN([DISTINCT] expr) 1.返回某列的最小值,忽略列值为NULL的行 SELECT MIN(prod_price) AS min_price FROM products; SUM([DISTINCT] expr) 1.返回某列值之和,忽略列值为NULL的行 SELECT SUM(item_price*quantity) AS

Views in Fragment are null

由 非 Y 不嫁゛ 提交于 2020-01-09 12:08:31
问题 Im still working on my Android App. Now im facing this problem: Code: package smoca.ch.kreagen.Fragments; import android.content.Context; import android.os.Bundle; import android.support.annotation.Nullable; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import io.realm.Realm; import io.realm.RealmQuery; import smoca.ch.kreagen.R; import smoca.ch.kreagen.models.Idea; public

Views in Fragment are null

由 谁说我不能喝 提交于 2020-01-09 12:06:11
问题 Im still working on my Android App. Now im facing this problem: Code: package smoca.ch.kreagen.Fragments; import android.content.Context; import android.os.Bundle; import android.support.annotation.Nullable; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import io.realm.Realm; import io.realm.RealmQuery; import smoca.ch.kreagen.R; import smoca.ch.kreagen.models.Idea; public

Why findViewById() is returning null if setcontentview() is not called?

由 女生的网名这么多〃 提交于 2020-01-09 11:52:29
问题 I am new-bee to android. Here is my xml file - <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity" android:id="@+id/linearlayout" android:orientation="vertical"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hello_world" android:id="@+id/textview" /> </LinearLayout>

Why findViewById() is returning null if setcontentview() is not called?

由 狂风中的少年 提交于 2020-01-09 11:51:53
问题 I am new-bee to android. Here is my xml file - <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity" android:id="@+id/linearlayout" android:orientation="vertical"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hello_world" android:id="@+id/textview" /> </LinearLayout>

SuperObject cannot handle null string

由 六月ゝ 毕业季﹏ 提交于 2020-01-09 11:24:11
问题 Some JSON serializers return null for an empty string datafield, e.g. { "searchtext": null, "moretext": "contains something", "bookdate": 1377468000000, "empid": 12345, "listtype": 1 } I'm using SuperObject to create a ISuperObject: var FJSONRequest: ISuperObject; then FJSONRequest := SO(Request.Content); // Webservice request This returns an object with a string containing the text 'null' . Obviously this is because SuperObject does not care about the quotes ( "searchtext": a gives the same
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