From c8e1d9ac5973985860ae78396ecc4073abce043c Mon Sep 17 00:00:00 2001
From: ZhouXY108 <luquanlion@outlook.com>
Date: Sun, 29 Dec 2024 22:07:05 +0800
Subject: [PATCH] =?UTF-8?q?CollectionTools=20=E6=96=B0=E5=A2=9E=20nullToEm?=
 =?UTF-8?q?ptyList=E3=80=81nullToEmptySet=E3=80=81nullToEmptyMap=20?=
 =?UTF-8?q?=E6=96=B9=E6=B3=95?=
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Content-Type: text/plain; charset=UTF-8
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`CollectionTools` 提供 `nullToEmptyList`、`nullToEmptySet`、`nullToEmptyMap`，分别在提供的集合为 `null` 时，返回 `Collections.emptyList()`、`Collections.emptySet()`、`Collections.emptyMap()`。

close #7
---
 .../commons/collection/CollectionTools.java   | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/main/java/xyz/zhouxy/plusone/commons/collection/CollectionTools.java b/src/main/java/xyz/zhouxy/plusone/commons/collection/CollectionTools.java
index d15aaee..f5e671b 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/collection/CollectionTools.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/collection/CollectionTools.java
@@ -17,8 +17,12 @@
 package xyz.zhouxy.plusone.commons.collection;
 
 import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
 /**
@@ -51,6 +55,21 @@ public class CollectionTools {
         return map != null && !map.isEmpty();
     }
 
+    @Nonnull
+    public static <T> List<T> nullToEmptyList(@Nullable List<T> list) {
+        return list == null ? Collections.emptyList() : list;
+    }
+
+    @Nonnull
+    public static <T> Set<T> nullToEmptySet(@Nullable Set<T> set) {
+        return set == null ? Collections.emptySet() : set;
+    }
+
+    @Nonnull
+    public static <K, V> Map<K, V> nullToEmptyMap(@Nullable Map<K, V> map) {
+        return map == null ? Collections.emptyMap() : map;
+    }
+
     private CollectionTools() {
         throw new IllegalStateException("Utility class");
     }