src/share/classes/java/util/StringJoiner.java
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@@ -1,7 +1,7 @@
/*
- * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
@@ -22,10 +22,13 @@
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.util;
+import sun.misc.JavaLangAccess;
+import sun.misc.SharedSecrets;
+
/**
* {@code StringJoiner} is used to construct a sequence of characters separated
* by a delimiter and optionally starting with a supplied prefix
* and ending with a supplied suffix.
* <p>
@@ -65,26 +68,28 @@
public final class StringJoiner {
private final String prefix;
private final String delimiter;
private final String suffix;
- /*
- * StringBuilder value -- at any time, the characters constructed from the
- * prefix, the added element separated by the delimiter, but without the
- * suffix, so that we can more easily add elements without having to jigger
- * the suffix each time.
- */
- private StringBuilder value;
-
- /*
- * By default, the string consisting of prefix+suffix, returned by
- * toString(), or properties of value, when no elements have yet been added,
- * i.e. when it is empty. This may be overridden by the user to be some
- * other value including the empty String.
+ /** Contains all the string components added so far. */
+ private String[] elts;
+
+ /** The number of string components added so far. */
+ private int size;
+
+ /** Total length in chars so far, excluding prefix and suffix. */
+ private int len;
+
+ /**
+ * When overriden by the user to be non-null via {@link setEmptyValue}, the
+ * string returned by toString() when no elements have yet been added.
+ * When null, prefix + suffix is used as the empty value.
*/
private String emptyValue;
+ private static final JavaLangAccess jla = SharedSecrets.getJavaLangAccess();
+
/**
* Constructs a {@code StringJoiner} with no characters in it, with no
* {@code prefix} or {@code suffix}, and a copy of the supplied
* {@code delimiter}.
* If no characters are added to the {@code StringJoiner} and methods
@@ -123,11 +128,10 @@
Objects.requireNonNull(suffix, "The suffix must not be null");
// make defensive copies of arguments
this.prefix = prefix.toString();
this.delimiter = delimiter.toString();
this.suffix = suffix.toString();
- this.emptyValue = this.prefix + this.suffix;
}
/**
* Sets the sequence of characters to be used when determining the string
* representation of this {@code StringJoiner} and no elements have been
@@ -146,45 +150,69 @@
this.emptyValue = Objects.requireNonNull(emptyValue,
"The empty value must not be null").toString();
return this;
}
+ private static int getChars(String s, char[] chars, int start) {
+ int len = s.length();
+ s.getChars(0, len, chars, start);
+ return len;
+ }
+
/**
* Returns the current value, consisting of the {@code prefix}, the values
* added so far separated by the {@code delimiter}, and the {@code suffix},
* unless no elements have been added in which case, the
- * {@code prefix + suffix} or the {@code emptyValue} characters are returned
+ * {@code prefix + suffix} or the {@code emptyValue} characters are returned.
*
* @return the string representation of this {@code StringJoiner}
*/
@Override
public String toString() {
- if (value == null) {
+ final String[] elts = this.elts;
+ if (elts == null && emptyValue != null) {
return emptyValue;
- } else {
- if (suffix.equals("")) {
- return value.toString();
- } else {
- int initialLength = value.length();
- String result = value.append(suffix).toString();
- // reset value to pre-append initialLength
- value.setLength(initialLength);
- return result;
}
+ final int size = this.size;
+ final int addLen = prefix.length() + suffix.length();
+ if (addLen == 0) {
+ compactElts();
+ return size == 0 ? "" : elts[0];
+ }
+ final String delimiter = this.delimiter;
+ final char[] chars = new char[len + addLen];
+ int k = getChars(prefix, chars, 0);
+ if (size > 0) {
+ k += getChars(elts[0], chars, k);
+ for (int i = 1; i < size; i++) {
+ k += getChars(delimiter, chars, k);
+ k += getChars(elts[i], chars, k);
}
}
+ k += getChars(suffix, chars, k);
+ return jla.newStringUnsafe(chars);
+ }
/**
* Adds a copy of the given {@code CharSequence} value as the next
* element of the {@code StringJoiner} value. If {@code newElement} is
* {@code null}, then {@code "null"} is added.
*
* @param newElement The element to add
* @return a reference to this {@code StringJoiner}
*/
public StringJoiner add(CharSequence newElement) {
- prepareBuilder().append(newElement);
+ final String elt = String.valueOf(newElement);
+ if (elts == null) {
+ elts = new String[8];
+ } else {
+ if (size == elts.length)
+ elts = Arrays.copyOf(elts, 2 * size);
+ len += delimiter.length();
+ }
+ len += elt.length();
+ elts[size++] = elt;
return this;
}
/**
* Adds the contents of the given {@code StringJoiner} without prefix and
@@ -205,28 +233,29 @@
* @throws NullPointerException if the other {@code StringJoiner} is null
* @return This {@code StringJoiner}
*/
public StringJoiner merge(StringJoiner other) {
Objects.requireNonNull(other);
- if (other.value != null) {
- final int length = other.value.length();
- // lock the length so that we can seize the data to be appended
- // before initiate copying to avoid interference, especially when
- // merge 'this'
- StringBuilder builder = prepareBuilder();
- builder.append(other.value, other.prefix.length(), length);
- }
+ if (other.elts == null) {
return this;
}
+ other.compactElts();
+ return add(other.elts[0]);
+ }
- private StringBuilder prepareBuilder() {
- if (value != null) {
- value.append(delimiter);
- } else {
- value = new StringBuilder().append(prefix);
+ private void compactElts() {
+ if (size > 1) {
+ final char[] chars = new char[len];
+ int i = 1, k = getChars(elts[0], chars, 0);
+ do {
+ k += getChars(delimiter, chars, k);
+ k += getChars(elts[i], chars, k);
+ elts[i] = null;
+ } while (++i < size);
+ size = 1;
+ elts[0] = jla.newStringUnsafe(chars);
}
- return value;
}
/**
* Returns the length of the {@code String} representation
* of this {@code StringJoiner}. Note that if
@@ -236,12 +265,9 @@
* {@code toString().length()}.
*
* @return the length of the current value of {@code StringJoiner}
*/
public int length() {
- // Remember that we never actually append the suffix unless we return
- // the full (present) value or some sub-string or length of it, so that
- // we can add on more if we need to.
- return (value != null ? value.length() + suffix.length() :
- emptyValue.length());
+ return (size == 0 && emptyValue != null) ? emptyValue.length() :
+ len + prefix.length() + suffix.length();
}
}