FoldExpressionIntoStream: support String.join-able patterns (IDEA-190570)

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/foldIntoStream/afterConcatIntegers.java

@@ -0,0 +1,9 @@
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+// "Fold expression into Stream chain" "true"
+class Test {
+  void test2(Integer a, Integer b, Integer c, Integer d) {
+    String result = Stream.of(a, b, c, d).map(String::valueOf).collect(Collectors.joining(",")) + ",";
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/foldIntoStream/afterConcatJoin.java

@@ -0,0 +1,6 @@
+// "Fold expression into 'String.join'" "true"
+class Test {
+  void test(String a, String b, String c, String d) {
+    String result = String.join(",", a, b, c, d) + ",";
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/foldIntoStream/beforeConcatIntegers.java

@@ -0,0 +1,6 @@
+// "Fold expression into Stream chain" "true"
+class Test {
+  void test2(Integer a, Integer b, Integer c, Integer d) {
+    String result = a + "," + b + "," + c + "," <caret>+ d + ",";
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/foldIntoStream/beforeConcatJoin.java

@@ -0,0 +1,6 @@
+// "Fold expression into 'String.join'" "true"
+class Test {
+  void test(String a, String b, String c, String d) {
+    String result = a + "," + b + "," + c + ","<caret> + d + ",";
+  }
+}