StreamApiMigrationInspection: suggest to use takeWhile() in Java-9

java/java-impl/src/com/intellij/codeInspection/streamMigration/StreamApiMigrationInspection.java

@@ -764,7 +764,12 @@ public class StreamApiMigrationInspection extends BaseJavaBatchLocalInspectionTo
       PsiExpression intermediate = makeIntermediateExpression(factory);
       PsiExpression expression =
         myNegated ? factory.createExpressionFromText(BoolUtils.getNegatedExpressionText(intermediate), myExpression) : intermediate;
-      return ".filter(" + LambdaUtil.createLambda(myVariable, expression) + ")";
+      return "." + getOpName() + "(" + LambdaUtil.createLambda(myVariable, expression) + ")";
+    }
+
+    @NotNull
+    String getOpName() {
+      return "filter";
     }
 
     PsiExpression makeIntermediateExpression(PsiElementFactory factory) {
@@ -772,6 +777,18 @@ public class StreamApiMigrationInspection extends BaseJavaBatchLocalInspectionTo
     }
   }
 
+  static class TakeWhileOp extends FilterOp {
+    TakeWhileOp(PsiExpression condition, PsiVariable variable, boolean negated) {
+      super(condition, variable, negated);
+    }
+
+    @NotNull
+    @Override
+    String getOpName() {
+      return "takeWhile";
+    }
+  }
+
   static class CompoundFilterOp extends FilterOp {
     private final FlatMapOp myFlatMapOp;
     private final PsiVariable myMatchVariable;

java/java-impl/src/com/intellij/codeInspection/streamMigration/TerminalBlock.java

@@ -186,6 +186,18 @@ class TerminalBlock {
     }
     if(myStatements.length >= 1) {
       PsiStatement first = myStatements[0];
+      if(PsiUtil.isLanguageLevel9OrHigher(first.getContainingFile()) && first instanceof PsiIfStatement) {
+        PsiIfStatement ifStatement = (PsiIfStatement)first;
+        PsiExpression condition = ifStatement.getCondition();
+        if(ifStatement.getElseBranch() == null && condition != null) {
+          PsiStatement thenStatement = ControlFlowUtils.stripBraces(ifStatement.getThenBranch());
+          if(ControlFlowUtils.statementBreaksLoop(thenStatement, getMainLoop())) {
+            TakeWhileOp op = new TakeWhileOp(condition, myVariable, true);
+            PsiStatement[] leftOver = Arrays.copyOfRange(myStatements, 1, myStatements.length);
+            return new TerminalBlock(this, op, myVariable, leftOver);
+          }
+        }
+      }
       // extract map
       if(first instanceof PsiDeclarationStatement) {
         PsiDeclarationStatement decl = (PsiDeclarationStatement)first;

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/afterTakeWhileJava9.java

@@ -0,0 +1,12 @@
+// "Replace with collect" "true"
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class Test {
+  public static void test(List<String> data) {
+      List<String> result = data.stream().takeWhile(s -> !s.isEmpty()).collect(Collectors.toList());
+      System.out.println(result);
+  }
+}

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

@@ -0,0 +1,17 @@
+// "Replace with collect" "false"
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Test {
+  public static void test(List<String> data) {
+    List<String> result = new ArrayList<>();
+    for(String s : da<caret>ta) {
+      if(s.isEmpty()) {
+        break;
+      }
+      result.add(s);
+    }
+    System.out.println(result);
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/beforeTakeWhileJava9.java

@@ -0,0 +1,17 @@
+// "Replace with collect" "true"
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Test {
+  public static void test(List<String> data) {
+    List<String> result = new ArrayList<>();
+    for(String s : da<caret>ta) {
+      if(s.isEmpty()) {
+        break;
+      }
+      result.add(s);
+    }
+    System.out.println(result);
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/quickFix/StreamApiMigrationInspectionTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2016 JetBrains s.r.o.
+ * Copyright 2000-2017 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@ package com.intellij.codeInsight.daemon.quickFix;
 
 import com.intellij.codeInspection.LocalInspectionTool;
 import com.intellij.codeInspection.streamMigration.StreamApiMigrationInspection;
+import com.intellij.pom.java.LanguageLevel;
 import org.jetbrains.annotations.NotNull;
 
 
@@ -31,6 +32,11 @@ public class StreamApiMigrationInspectionTest extends LightQuickFixParameterized
     };
   }
 
+  @Override
+  protected LanguageLevel getLanguageLevel() {
+    return getTestName(false).contains("Java9") ? LanguageLevel.JDK_1_9 : LanguageLevel.JDK_1_8;
+  }
+
   public void test() throws Exception { doAllTests(); }
 
   @Override