Day093

README.adoc

@@ -3516,4 +3516,42 @@ public class Day092 {
         System.out.println(sum);
     }
 }
+----
+
+== Day 93 - Never return `null` in a method that has a `Collection` as return type.
+[source,java]
+----
+package com.thegreatapi.ahundreddaysofjava.day093;
+
+import java.time.Instant;
+import java.time.temporal.ChronoField;
+import java.util.List;
+
+public class Day093 {
+
+    public static void main(String[] args) {
+        List<String> myList = getList();
+
+        // If myList is null, a NullPointerException will be thrown
+        for (String s : myList) {
+            System.out.println(s);
+        }
+    }
+
+    private static List<String> getList() {
+        if (someCondition()) {
+            return List.of("a", "b", "c");
+        } else {
+//          Instead of returning null
+//          return null;
+
+//          Return an empty list, so the caller don't need to check if the returned list is not null
+            return List.of();
+        }
+    }
+
+    private static boolean someCondition() {
+        return Instant.now().get(ChronoField.MILLI_OF_SECOND) % 2 == 0;
+    }
+}
 ----

days/day093/pom.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>days</artifactId>
+        <groupId>com.thegreatapi.100daysofjava</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>day093</artifactId>
+
+    <properties>
+        <maven.compiler.source>16</maven.compiler.source>
+        <maven.compiler.target>16</maven.compiler.target>
+    </properties>
+
+</project>

days/day093/src/main/java/com/thegreatapi/ahundreddaysofjava/day093/Day093.java

@@ -0,0 +1,33 @@
+package com.thegreatapi.ahundreddaysofjava.day093;
+
+import java.time.Instant;
+import java.time.temporal.ChronoField;
+import java.util.List;
+
+public class Day093 {
+
+    public static void main(String[] args) {
+        List<String> myList = getList();
+
+        // If myList is null, a NullPointerException will be thrown
+        for (String s : myList) {
+            System.out.println(s);
+        }
+    }
+
+    private static List<String> getList() {
+        if (someCondition()) {
+            return List.of("a", "b", "c");
+        } else {
+//          Instead of returning null
+//          return null;
+
+//          Return an empty list, so the caller don't need to check if the returned list is not null
+            return List.of();
+        }
+    }
+
+    private static boolean someCondition() {
+        return Instant.now().get(ChronoField.MILLI_OF_SECOND) % 2 == 0;
+    }
+}

days/pom.xml

@@ -103,6 +103,7 @@
         <module>day090</module>
         <module>day091</module>
         <module>day092</module>
+        <module>day093</module>
     </modules>
 
 </project>