IDEA-167088 Stream API migration: support simple joining cases

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/afterJoining.java

@@ -0,0 +1,13 @@
+// "Replace with collect" "true"
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class Test {
+  static String test(List<String> list) {
+    String sb;
+    System.out.println("hello");
+      sb = list.stream().filter(s -> !s.isEmpty()).collect(Collectors.joining());
+    return sb.length() == 0 ? null : sb;
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/afterJoiningAssign.java

@@ -0,0 +1,12 @@
+// "Replace with collect" "true"
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class Test {
+  static String test(List<String> list) {
+      String sb = list.stream().filter(s -> !s.isEmpty()).collect(Collectors.joining());
+      String s = sb;
+    return s.trim();
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/beforeJoining.java

@@ -0,0 +1,16 @@
+// "Replace with collect" "true"
+
+import java.util.List;
+
+public class Test {
+  static String test(List<String> list) {
+    StringBuilder sb = new StringBuilder();
+    System.out.println("hello");
+    for(String s : li<caret>st) {
+      if(!s.isEmpty()) {
+        sb.append(s);
+      }
+    }
+    return sb.length() == 0 ? null : sb.toString();
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/beforeJoiningAssign.java

@@ -0,0 +1,16 @@
+// "Replace with collect" "true"
+
+import java.util.List;
+
+public class Test {
+  static String test(List<String> list) {
+    StringBuffer sb = new StringBuffer();
+    for(String s : li<caret>st) {
+      if(!s.isEmpty()) {
+        sb.append(s);
+      }
+    }
+    String s = sb.toString();
+    return s.trim();
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/beforeJoiningStringBuilderReused.java

@@ -0,0 +1,17 @@
+// "Replace with collect" "false"
+
+import java.util.List;
+
+public class Test {
+  static String test(List<String> list) {
+    StringBuilder sb = new StringBuilder();
+    System.out.println("hello");
+    for(String s : li<caret>st) {
+      if(!s.isEmpty()) {
+        sb.append(s);
+      }
+    }
+    sb.append("xyz");
+    return sb.toString();
+  }
+}