Java8MapApiInspection: better name generation for lambda argument (IDEA-CR-16359)

java/java-impl/src/com/intellij/codeInspection/java18api/Java8MapApiInspection.java

@@ -29,7 +29,6 @@ import com.intellij.psi.search.searches.ReferencesSearch;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.psi.util.PsiUtil;
 import com.siyeh.ig.psiutils.*;
-import one.util.streamex.IntStreamEx;
 import one.util.streamex.StreamEx;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.Nls;
@@ -383,13 +382,7 @@ public class Java8MapApiInspection extends BaseJavaBatchLocalInspectionTool {
               refs = StreamEx.of(PsiTreeUtil.collectElementsOfType(value, PsiReferenceExpression.class))
                 .filter(ref -> ref.getQualifierExpression() == null && ref.isReferenceTo(element)).toList();
               if (!refs.isEmpty()) {
-                String name = ((PsiReferenceExpression)key).getReferenceName();
-                // like "myVariableName" => "mvn"
-                nameCandidate = IntStreamEx.ofChars(name).mapFirst(Character::toUpperCase).filter(Character::isUpperCase).charsToString()
-                  .toLowerCase(Locale.ENGLISH);
-                if (nameCandidate.isEmpty()) {
-                  nameCandidate = "k";
-                }
+                nameCandidate = getNameCandidate(((PsiReferenceExpression)key).getReferenceName());
               }
             }
           }
@@ -418,6 +411,29 @@ public class Java8MapApiInspection extends BaseJavaBatchLocalInspectionTool {
       }
       CodeStyleManager.getInstance(project).reformat(result);
     }
+
+    @NotNull
+    private static String getNameCandidate(String name) {
+      // Either last uppercase letter (if it's not the last letter) or the first letter, removing leading underscores
+      // token -> t
+      // myAccessToken -> t
+      // SQL -> s
+      // __name -> n
+      // __1 -> k
+      String nameCandidate;
+      name = name.replaceFirst("^[_\\d]+", "");
+      if (name.isEmpty()) return "k";
+      nameCandidate = name.substring(0, 1);
+      for (int pos = name.length() - 1; pos > 0; pos--) {
+        if (Character.isUpperCase(name.charAt(pos))) {
+          if (pos != name.length() - 1) {
+            nameCandidate = name.substring(pos, pos + 1);
+          }
+          break;
+        }
+      }
+      return nameCandidate.toLowerCase(Locale.ENGLISH);
+    }
   }
 
   class MapCheckCondition {

java/java-tests/testData/inspection/java8MapApi/afterComputeIfAbsentUsedKeyTwoWords.java

@@ -0,0 +1,21 @@
+// "Replace with 'computeIfAbsent' method call" "true"
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class Main {
+  static class MyItem {
+    String k;
+    int i;
+
+    MyItem(String k, int i) {
+      this.k = k;
+      this.i = i;
+    }
+  }
+
+  public MyItem testMap(Map<String, MyItem> map, String localUser) {
+      MyItem item = map.computeIfAbsent(localUser, u -> new MyItem(u, 1));
+      return item;
+  }
+}

java/java-tests/testData/inspection/java8MapApi/afterComputeIfAbsentUsedKeyUnderscores.java

@@ -0,0 +1,21 @@
+// "Replace with 'computeIfAbsent' method call" "true"
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class Main {
+  static class MyItem {
+    String k;
+    int i;
+
+    MyItem(String k, int i) {
+      this.k = k;
+      this.i = i;
+    }
+  }
+
+  public MyItem testMap(Map<String, MyItem> map, String ___1) {
+      MyItem item = map.computeIfAbsent(___1, k -> new MyItem(k, 1));
+      return item;
+  }
+}

java/java-tests/testData/inspection/java8MapApi/beforeComputeIfAbsentUsedKeyTwoWords.java

@@ -0,0 +1,24 @@
+// "Replace with 'computeIfAbsent' method call" "true"
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class Main {
+  static class MyItem {
+    String k;
+    int i;
+
+    MyItem(String k, int i) {
+      this.k = k;
+      this.i = i;
+    }
+  }
+
+  public MyItem testMap(Map<String, MyItem> map, String localUser) {
+    MyItem item = map.get(localUser);
+    if(item == nul<caret>l) {
+      map.put(localUser, item = new MyItem(localUser, 1));
+    }
+    return item;
+  }
+}

java/java-tests/testData/inspection/java8MapApi/beforeComputeIfAbsentUsedKeyUnderscores.java

@@ -0,0 +1,24 @@
+// "Replace with 'computeIfAbsent' method call" "true"
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class Main {
+  static class MyItem {
+    String k;
+    int i;
+
+    MyItem(String k, int i) {
+      this.k = k;
+      this.i = i;
+    }
+  }
+
+  public MyItem testMap(Map<String, MyItem> map, String ___1) {
+    MyItem item = map.get(___1);
+    if(item == nul<caret>l) {
+      map.put(___1, item = new MyItem(___1, 1));
+    }
+    return item;
+  }
+}