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Fix #4872: Implement java.util.StringJoiner.
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‎javalib/src/main/scala/java/util/StringJoiner.scala

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/*
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* Scala.js (https://www.scala-js.org/)
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*
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* Copyright EPFL.
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*
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* Licensed under Apache License 2.0
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* (https://www.apache.org/licenses/LICENSE-2.0).
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*
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* See the NOTICE file distributed with this work for
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* additional information regarding copyright ownership.
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*/
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package java.util
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@inline
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final class StringJoiner private (delimiter: String, prefix: String, suffix: String) extends AnyRef {
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/** The custom value to return if empty, set by `setEmptyValue` (nullable).
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*
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* If `null`, defaults to `prefix + suffix`.
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*/
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private var emptyValue: String = null
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/** The current value, excluding prefix and suffix. */
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private var value: String = ""
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/** Whether the string joiner is currently empty. */
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private var isEmpty: Boolean = true
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def this(delimiter: CharSequence) =
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this(delimiter.toString(), "", "")
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def this(delimiter: CharSequence, prefix: CharSequence, suffix: CharSequence) =
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this(delimiter.toString(), prefix.toString(), suffix.toString())
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def setEmptyValue(emptyValue: CharSequence): StringJoiner = {
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this.emptyValue = emptyValue.toString()
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this
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}
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override def toString(): String =
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if (isEmpty && emptyValue != null) emptyValue
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else prefix + value + suffix
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def add(newElement: CharSequence): StringJoiner = {
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if (isEmpty)
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isEmpty = false
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else
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value += delimiter
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value += newElement // if newElement is null, adds "null"
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this
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}
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def merge(other: StringJoiner): StringJoiner = {
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if (!other.isEmpty) // if `other` is empty, `merge` has no effect
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add(other.value) // without prefix nor suffix, but with delimiters
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this
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}
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def length(): Int =
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if (isEmpty && emptyValue != null) emptyValue.length()
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else prefix.length() + value.length() + suffix.length()
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}

‎test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/StringJoinerTest.scala

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/*
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* Scala.js (https://www.scala-js.org/)
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*
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* Copyright EPFL.
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*
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* Licensed under Apache License 2.0
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* (https://www.apache.org/licenses/LICENSE-2.0).
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*
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* See the NOTICE file distributed with this work for
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* additional information regarding copyright ownership.
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*/
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package org.scalajs.testsuite.javalib.util
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import java.nio.CharBuffer
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import java.util.StringJoiner
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import org.junit.Assert._
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import org.junit.Assume._
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import org.junit.Test
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import org.scalajs.testsuite.utils.AssertThrows.assertThrows
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import org.scalajs.testsuite.utils.Platform
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class StringJoinerTest {
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import StringJoinerTest._
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@Test def testEmpty(): Unit = {
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assertJoinerResult("")(new StringJoiner(","))
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assertJoinerResult("[]")(new StringJoiner(";", "[", "]"))
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assertJoinerResult("--")(new StringJoiner(";").setEmptyValue("--"))
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assertJoinerResult("--")(new StringJoiner(";", "[", "]").setEmptyValue("--"))
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}
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@Test def testNonEmpty(): Unit = {
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assertJoinerResult("one") {
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new StringJoiner(",").add("one")
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}
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assertJoinerResult("one,two,three") {
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new StringJoiner(",").add("one").add("two").add("three")
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}
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assertJoinerResult("[one, two, three]") {
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new StringJoiner(", ", "[", "]").add("one").add("two").add("three")
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}
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assertJoinerResult("[one, null, three]") {
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new StringJoiner(", ", "[", "]").add("one").add(null).add("three")
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}
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assertJoinerResult("[one, two, three]") {
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new StringJoiner(", ", "[", "]").add("one").add(CharBuffer.wrap("two")).add("three")
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}
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assertJoinerResult("") {
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new StringJoiner(",").add("")
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}
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assertJoinerResult("one,") {
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new StringJoiner(",").add("one").add("")
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}
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assertJoinerResult(",two") {
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new StringJoiner(",").add("").add("two")
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}
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assertJoinerResult("one,,three") {
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new StringJoiner(",").add("one").add("").add("three")
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}
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assertJoinerResult("one") {
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new StringJoiner(",").setEmptyValue("--").add("one")
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}
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assertJoinerResult("one,two,three") {
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new StringJoiner(",").setEmptyValue("--").add("one").add("two").add("three")
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}
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assertJoinerResult("[one, two, three]") {
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new StringJoiner(", ", "[", "]").add("one").add("two").setEmptyValue("--").add("three")
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}
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assertJoinerResult("[one, two, three]") {
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new StringJoiner(", ", "[", "]").add("one").add("two").add("three").setEmptyValue("--")
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}
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assertJoinerResult("") {
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new StringJoiner(",").setEmptyValue("--").add("")
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}
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assertJoinerResult("one,") {
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new StringJoiner(",").setEmptyValue("--").add("one").add("")
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}
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}
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@Test def testMerge(): Unit = {
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val empty = new StringJoiner(";", "[", "]").setEmptyValue("--")
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val single = new StringJoiner(";", "[", "]").setEmptyValue("--").add("single")
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val multiple = new StringJoiner(";", "[", "]").setEmptyValue("--").add("a").add("b").add("c")
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val singleBlank = new StringJoiner(";", "[", "]").setEmptyValue("--").add("")
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assertJoinerResult("+++") {
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new StringJoiner(", ", "{", "}").merge(empty).setEmptyValue("+++")
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}
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assertJoinerResult("+++") {
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new StringJoiner(", ", "{", "}").setEmptyValue("+++").merge(empty)
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}
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assertJoinerResult("{}") {
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new StringJoiner(", ", "{", "}").merge(singleBlank).setEmptyValue("+++")
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}
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assertJoinerResult("{}") {
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new StringJoiner(", ", "{", "}").setEmptyValue("+++").merge(singleBlank)
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}
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assertJoinerResult("{one, two}") {
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new StringJoiner(", ", "{", "}").add("one").merge(empty).add("two")
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}
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assertJoinerResult("{one, single, two}") {
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new StringJoiner(", ", "{", "}").add("one").merge(single).add("two")
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}
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assertJoinerResult("{one, a;b;c, two}") {
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new StringJoiner(", ", "{", "}").add("one").merge(multiple).add("two")
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}
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assertJoinerResult("{one, , two}") {
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new StringJoiner(", ", "{", "}").add("one").merge(singleBlank).add("two")
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}
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assertJoinerResult("{single}") {
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new StringJoiner(", ", "{", "}").merge(single)
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}
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assertJoinerResult("{a;b;c}") {
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new StringJoiner(", ", "{", "}").merge(multiple)
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}
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assertJoinerResult("{}") {
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new StringJoiner(", ", "{", "}").merge(singleBlank)
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}
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}
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@Test def testState(): Unit = {
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val mutableCharSeq = CharBuffer.allocate(2).put(0, '?').put(1, '!')
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val joiner = new StringJoiner(mutableCharSeq, mutableCharSeq, mutableCharSeq)
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assertJoinerResult("?!?!")(joiner)
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joiner.setEmptyValue(mutableCharSeq)
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assertJoinerResult("?!")(joiner)
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mutableCharSeq.put(0, '-')
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assertJoinerResult("?!")(joiner) // the previously set emptyValue is not affected
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joiner.setEmptyValue(mutableCharSeq)
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assertJoinerResult("-!")(joiner)
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joiner.add("one")
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assertJoinerResult("?!one?!")(joiner) // the previously set prefix and suffix are not affected
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joiner.add("two")
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assertJoinerResult("?!one?!two?!")(joiner) // the previously set delimiter is not affected
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}
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@Test def testNPE(): Unit = {
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assumeTrue("requires compliant null pointers", Platform.hasCompliantNullPointers)
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@noinline
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def assertNPE[U](code: => U): Unit =
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assertThrows(classOf[NullPointerException], code)
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assertNPE(new StringJoiner(null))
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assertNPE(new StringJoiner(null, "[", "]"))
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assertNPE(new StringJoiner(",", null, "]"))
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assertNPE(new StringJoiner(",", "[", null))
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assertNPE(new StringJoiner(",").setEmptyValue(null))
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assertNPE(new StringJoiner(",").merge(null))
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}
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}
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object StringJoinerTest {
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def assertJoinerResult(expected: String)(joiner: StringJoiner): Unit = {
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assertEquals(expected, joiner.toString())
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assertEquals(expected.length(), joiner.length())
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}
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}

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