[java-shib-shared] 02/02: Add zero-arg and one-arg listOf and setOf

[Ian Young]

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iay pushed a commit to branch main
in repository java-shib-shared.

View the commit online:
http://git.shibboleth.net/view/?p=java-shib-shared.git;a=commit;h=893324fec4839311bf172b805bce650fdfa601db

commit 893324fec4839311bf172b805bce650fdfa601db
Author: Ian Young <ian at iay.org.uk>
AuthorDate: Tue Apr 4 07:08:31 2023 +0100

    Add zero-arg and one-arg listOf and setOf
    
    These might seem superfluous, as we also have "empty" and "singleton" variants. The use case is
    direct conversion from the equivalent, more modern, List.of(), List.of(x), etc.; if we don't implement
    ofList() etc. we run the risk of accidentally and silently interposing e.g. the worst possible empty
    list constructor involving varargs array construction.
---
 .../shared/collection/CollectionSupport.java       | 50 ++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/shib-support/src/main/java/net/shibboleth/shared/collection/CollectionSupport.java b/shib-support/src/main/java/net/shibboleth/shared/collection/CollectionSupport.java
index 2091ae2e..f8634e33 100644
--- a/shib-support/src/main/java/net/shibboleth/shared/collection/CollectionSupport.java
+++ b/shib-support/src/main/java/net/shibboleth/shared/collection/CollectionSupport.java
@@ -121,6 +121,31 @@ public final class CollectionSupport {
         return Collections.singletonList(item);
     }
 
+    /**
+     * Gets a zero member list with non-null guarantee.
+     * 
+     * @param <T> list type
+     *
+     * @return zero member list
+     */
+    @SuppressWarnings("null")
+    @Nonnull @Unmodifiable @NotLive public static <T> List<T> listOf() {
+        return List.of();
+    }
+
+    /**
+     * Gets a one member list with non-null guarantee.
+     * 
+     * @param <T> list type
+     * @param second the second item
+     *
+     * @return two member list
+     */
+    @SuppressWarnings("null")
+    @Nonnull @Unmodifiable @NotLive public static <T> List<T> listOf(@Nonnull final T first) {
+        return List.of(first);
+    }
+
     /**
      * Gets a two member list with non-null guarantee.
      * 
@@ -189,6 +214,31 @@ public final class CollectionSupport {
         return Collections.singleton(item);
     }
 
+    /**
+     * Gets a zero member set with non-null guarantee.
+     *
+     * @param <T> list type
+     *
+     * @return zero member set
+     */
+    @SuppressWarnings("null")
+    @Nonnull @Unmodifiable @NotLive public static <T> Set<T> setOf() {
+        return Set.of();
+    }
+
+    /**
+     * Gets a one member set with non-null guarantee.
+     *
+     * @param <T> list type
+     * @param first the first item
+     *
+     * @return one member set
+     */
+    @SuppressWarnings("null")
+    @Nonnull @Unmodifiable @NotLive public static <T> Set<T> setOf(@Nonnull final T first) {
+        return Set.of(first);
+    }
+
     /**
      * Gets a two member set with non-null guarantee.
      *

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