Java example source code file (Longs.java)
The Longs.java Java example source code/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.common.primitives;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Converter;
import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;
import javax.annotation.CheckForNull;
import javax.annotation.Nullable;
/**
* Static utility methods pertaining to {@code long} primitives, that are not already found in
* either {@link Long} or {@link Arrays}.
*
* <p>See the Guava User Guide article on
* <a href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities.
*
* @author Kevin Bourrillion
* @since 1.0
*/
@GwtCompatible
public final class Longs {
private Longs() {}
/**
* The number of bytes required to represent a primitive {@code long} value.
*/
public static final int BYTES = Long.SIZE / Byte.SIZE;
/**
* The largest power of two that can be represented as a {@code long}.
*
* @since 10.0
*/
public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2);
/**
* Returns a hash code for {@code value}; equal to the result of invoking
* {@code ((Long) value).hashCode()}.
*
* <p>This method always return the value specified by {@link Long#hashCode()} in java, which
* might be different from {@code ((Long) value).hashCode()} in GWT because
* {@link Long#hashCode()} in GWT does not obey the JRE contract.
*
* @param value a primitive {@code long} value
* @return a hash code for the value
*/
public static int hashCode(long value) {
return (int) (value ^ (value >>> 32));
}
/**
* Compares the two specified {@code long} values. The sign of the value returned is the same as
* that of {@code ((Long) a).compareTo(b)}.
*
* <p>Note for Java 7 and later: this method should be treated as deprecated; use the
* equivalent {@link Long#compare} method instead.
*
* @param a the first {@code long} to compare
* @param b the second {@code long} to compare
* @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
* greater than {@code b}; or zero if they are equal
*/
public static int compare(long a, long b) {
return (a < b) ? -1 : ((a > b) ? 1 : 0);
}
/**
* Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
*
* @param array an array of {@code long} values, possibly empty
* @param target a primitive {@code long} value
* @return {@code true} if {@code array[i] == target} for some value of {@code
* i}
*/
public static boolean contains(long[] array, long target) {
for (long value : array) {
if (value == target) {
return true;
}
}
return false;
}
/**
* Returns the index of the first appearance of the value {@code target} in {@code array}.
*
* @param array an array of {@code long} values, possibly empty
* @param target a primitive {@code long} value
* @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
* such index exists.
*/
public static int indexOf(long[] array, long target) {
return indexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int indexOf(long[] array, long target, int start, int end) {
for (int i = start; i < end; i++) {
if (array[i] == target) {
return i;
}
}
return -1;
}
/**
* Returns the start position of the first occurrence of the specified {@code
* target} within {@code array}, or {@code -1} if there is no such occurrence.
*
* <p>More formally, returns the lowest index {@code i} such that
* {@code Arrays.copyOfRange(array, i, i + target.length)} contains exactly the same elements as
* {@code target}.
*
* @param array the array to search for the sequence {@code target}
* @param target the array to search for as a sub-sequence of {@code array}
*/
public static int indexOf(long[] array, long[] target) {
checkNotNull(array, "array");
checkNotNull(target, "target");
if (target.length == 0) {
return 0;
}
outer:
for (int i = 0; i < array.length - target.length + 1; i++) {
for (int j = 0; j < target.length; j++) {
if (array[i + j] != target[j]) {
continue outer;
}
}
return i;
}
return -1;
}
/**
* Returns the index of the last appearance of the value {@code target} in {@code array}.
*
* @param array an array of {@code long} values, possibly empty
* @param target a primitive {@code long} value
* @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
* such index exists.
*/
public static int lastIndexOf(long[] array, long target) {
return lastIndexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int lastIndexOf(long[] array, long target, int start, int end) {
for (int i = end - 1; i >= start; i--) {
if (array[i] == target) {
return i;
}
}
return -1;
}
/**
* Returns the least value present in {@code array}.
*
* @param array a <i>nonempty array of {@code long} values
* @return the value present in {@code array} that is less than or equal to every other value in
* the array
* @throws IllegalArgumentException if {@code array} is empty
*/
public static long min(long... array) {
checkArgument(array.length > 0);
long min = array[0];
for (int i = 1; i < array.length; i++) {
if (array[i] < min) {
min = array[i];
}
}
return min;
}
/**
* Returns the greatest value present in {@code array}.
*
* @param array a <i>nonempty array of {@code long} values
* @return the value present in {@code array} that is greater than or equal to every other value
* in the array
* @throws IllegalArgumentException if {@code array} is empty
*/
public static long max(long... array) {
checkArgument(array.length > 0);
long max = array[0];
for (int i = 1; i < array.length; i++) {
if (array[i] > max) {
max = array[i];
}
}
return max;
}
/**
* Returns the values from each provided array combined into a single array. For example,
* {@code concat(new long[] {a, b}, new long[] {}, new long[] {c}} returns the array
* {@code {a, b, c}}.
*
* @param arrays zero or more {@code long} arrays
* @return a single array containing all the values from the source arrays, in order
*/
public static long[] concat(long[]... arrays) {
int length = 0;
for (long[] array : arrays) {
length += array.length;
}
long[] result = new long[length];
int pos = 0;
for (long[] array : arrays) {
System.arraycopy(array, 0, result, pos, array.length);
pos += array.length;
}
return result;
}
/**
* Returns a big-endian representation of {@code value} in an 8-element byte array; equivalent to
* {@code ByteBuffer.allocate(8).putLong(value).array()}. For example, the input value
* {@code 0x1213141516171819L} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16,
* 0x17, 0x18, 0x19}}.
*
* <p>If you need to convert and concatenate several values (possibly even of different types),
* use a shared {@link java.nio.ByteBuffer} instance, or use
* {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer.
*/
public static byte[] toByteArray(long value) {
// Note that this code needs to stay compatible with GWT, which has known
// bugs when narrowing byte casts of long values occur.
byte[] result = new byte[8];
for (int i = 7; i >= 0; i--) {
result[i] = (byte) (value & 0xffL);
value >>= 8;
}
return result;
}
/**
* Returns the {@code long} value whose big-endian representation is stored in the first 8 bytes
* of {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getLong()}. For example, the
* input byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the
* {@code long} value {@code 0x1213141516171819L}.
*
* <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more
* flexibility at little cost in readability.
*
* @throws IllegalArgumentException if {@code bytes} has fewer than 8 elements
*/
public static long fromByteArray(byte[] bytes) {
checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES);
return fromBytes(
bytes[0], bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7]);
}
/**
* Returns the {@code long} value whose byte representation is the given 8 bytes, in big-endian
* order; equivalent to {@code Longs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8})}.
*
* @since 7.0
*/
public static long fromBytes(
byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8) {
return (b1 & 0xFFL) << 56
| (b2 & 0xFFL) << 48
| (b3 & 0xFFL) << 40
| (b4 & 0xFFL) << 32
| (b5 & 0xFFL) << 24
| (b6 & 0xFFL) << 16
| (b7 & 0xFFL) << 8
| (b8 & 0xFFL);
}
private static final byte[] asciiDigits = createAsciiDigits();
private static byte[] createAsciiDigits() {
byte[] result = new byte[128];
Arrays.fill(result, (byte) -1);
for (int i = 0; i <= 9; i++) {
result['0' + i] = (byte) i;
}
for (int i = 0; i <= 26; i++) {
result['A' + i] = (byte) (10 + i);
result['a' + i] = (byte) (10 + i);
}
return result;
}
private static int digit(char c) {
return (c < 128) ? asciiDigits[c] : -1;
}
/**
* Parses the specified string as a signed decimal long value. The ASCII character {@code '-'}
* (<code>'\u002D') is recognized as the minus sign.
*
* <p>Unlike {@link Long#parseLong(String)}, this method returns {@code null} instead of throwing
* an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returns
* {@code null} if non-ASCII digits are present in the string.
*
* <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
* the change to {@link Long#parseLong(String)} for that version.
*
* @param string the string representation of a long value
* @return the long value represented by {@code string}, or {@code null} if {@code string} has a
* length of zero or cannot be parsed as a long value
* @since 14.0
*/
@Beta
@Nullable
@CheckForNull
public static Long tryParse(String string) {
return tryParse(string, 10);
}
/**
* Parses the specified string as a signed long value using the specified radix. The ASCII
* character {@code '-'} (<code>'\u002D') is recognized as the minus sign.
*
* <p>Unlike {@link Long#parseLong(String, int)}, this method returns {@code null} instead of
* throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
* and returns {@code null} if non-ASCII digits are present in the string.
*
* <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
* the change to {@link Long#parseLong(String, int)} for that version.
*
* @param string the string representation of an long value
* @param radix the radix to use when parsing
* @return the long value represented by {@code string} using {@code radix}, or {@code null} if
* {@code string} has a length of zero or cannot be parsed as a long value
* @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or
* {@code radix > Character.MAX_RADIX}
* @since 19.0
*/
@Beta
@Nullable
@CheckForNull
public static Long tryParse(String string, int radix) {
if (checkNotNull(string).isEmpty()) {
return null;
}
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
throw new IllegalArgumentException(
"radix must be between MIN_RADIX and MAX_RADIX but was " + radix);
}
boolean negative = string.charAt(0) == '-';
int index = negative ? 1 : 0;
if (index == string.length()) {
return null;
}
int digit = digit(string.charAt(index++));
if (digit < 0 || digit >= radix) {
return null;
}
long accum = -digit;
long cap = Long.MIN_VALUE / radix;
while (index < string.length()) {
digit = digit(string.charAt(index++));
if (digit < 0 || digit >= radix || accum < cap) {
return null;
}
accum *= radix;
if (accum < Long.MIN_VALUE + digit) {
return null;
}
accum -= digit;
}
if (negative) {
return accum;
} else if (accum == Long.MIN_VALUE) {
return null;
} else {
return -accum;
}
}
private static final class LongConverter extends Converter<String, Long> implements Serializable {
static final LongConverter INSTANCE = new LongConverter();
@Override
protected Long doForward(String value) {
return Long.decode(value);
}
@Override
protected String doBackward(Long value) {
return value.toString();
}
@Override
public String toString() {
return "Longs.stringConverter()";
}
private Object readResolve() {
return INSTANCE;
}
private static final long serialVersionUID = 1;
}
/**
* Returns a serializable converter object that converts between strings and longs using
* {@link Long#decode} and {@link Long#toString()}. The returned converter throws
* {@link NumberFormatException} if the input string is invalid.
*
* <p>Warning: please see {@link Long#decode} to understand exactly how strings are parsed.
* For example, the string {@code "0123"} is treated as <i>octal and converted to the value
* {@code 83L}.
*
* @since 16.0
*/
@Beta
public static Converter<String, Long> stringConverter() {
return LongConverter.INSTANCE;
}
/**
* Returns an array containing the same values as {@code array}, but guaranteed to be of a
* specified minimum length. If {@code array} already has a length of at least {@code minLength},
* it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
* returned, containing the values of {@code array}, and zeroes in the remaining places.
*
* @param array the source array
* @param minLength the minimum length the returned array must guarantee
* @param padding an extra amount to "grow" the array by if growth is necessary
* @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
* @return an array containing the values of {@code array}, with guaranteed minimum length
* {@code minLength}
*/
public static long[] ensureCapacity(long[] array, int minLength, int padding) {
checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
checkArgument(padding >= 0, "Invalid padding: %s", padding);
return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
}
/**
* Returns a string containing the supplied {@code long} values separated by {@code separator}.
* For example, {@code join("-", 1L, 2L, 3L)} returns the string {@code "1-2-3"}.
*
* @param separator the text that should appear between consecutive values in the resulting string
* (but not at the start or end)
* @param array an array of {@code long} values, possibly empty
*/
public static String join(String separator, long... array) {
checkNotNull(separator);
if (array.length == 0) {
return "";
}
// For pre-sizing a builder, just get the right order of magnitude
StringBuilder builder = new StringBuilder(array.length * 10);
builder.append(array[0]);
for (int i = 1; i < array.length; i++) {
builder.append(separator).append(array[i]);
}
return builder.toString();
}
/**
* Returns a comparator that compares two {@code long} arrays <a
* href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
* compares, using {@link #compare(long, long)}), the first pair of values that follow any common
* prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
* example, {@code [] < [1L] < [1L, 2L] < [2L]}.
*
* <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
* support only identity equality), but it is consistent with
* {@link Arrays#equals(long[], long[])}.
*
* @since 2.0
*/
public static Comparator<long[]> lexicographicalComparator() {
return LexicographicalComparator.INSTANCE;
}
private enum LexicographicalComparator implements Comparator<long[]> {
INSTANCE;
@Override
public int compare(long[] left, long[] right) {
int minLength = Math.min(left.length, right.length);
for (int i = 0; i < minLength; i++) {
int result = Longs.compare(left[i], right[i]);
if (result != 0) {
return result;
}
}
return left.length - right.length;
}
@Override
public String toString() {
return "Longs.lexicographicalComparator()";
}
}
/**
* Returns an array containing each value of {@code collection}, converted to a {@code long} value
* in the manner of {@link Number#longValue}.
*
* <p>Elements are copied from the argument collection as if by {@code
* collection.toArray()}. Calling this method is as thread-safe as calling that method.
*
* @param collection a collection of {@code Number} instances
* @return an array containing the same values as {@code collection}, in the same order, converted
* to primitives
* @throws NullPointerException if {@code collection} or any of its elements is null
* @since 1.0 (parameter was {@code Collection<Long>} before 12.0)
*/
public static long[] toArray(Collection<? extends Number> collection) {
if (collection instanceof LongArrayAsList) {
return ((LongArrayAsList) collection).toLongArray();
}
Object[] boxedArray = collection.toArray();
int len = boxedArray.length;
long[] array = new long[len];
for (int i = 0; i < len; i++) {
// checkNotNull for GWT (do not optimize)
array[i] = ((Number) checkNotNull(boxedArray[i])).longValue();
}
return array;
}
/**
* Returns a fixed-size list backed by the specified array, similar to
* {@link Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any
* attempt to set a value to {@code null} will result in a {@link NullPointerException}.
*
* <p>The returned list maintains the values, but not the identities, of {@code Long} objects
* written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
* the returned list is unspecified.
*
* @param backingArray the array to back the list
* @return a list view of the array
*/
public static List<Long> asList(long... backingArray) {
if (backingArray.length == 0) {
return Collections.emptyList();
}
return new LongArrayAsList(backingArray);
}
@GwtCompatible
private static class LongArrayAsList extends AbstractList<Long>
implements RandomAccess, Serializable {
final long[] array;
final int start;
final int end;
LongArrayAsList(long[] array) {
this(array, 0, array.length);
}
LongArrayAsList(long[] array, int start, int end) {
this.array = array;
this.start = start;
this.end = end;
}
@Override
public int size() {
return end - start;
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public Long get(int index) {
checkElementIndex(index, size());
return array[start + index];
}
@Override
public boolean contains(Object target) {
// Overridden to prevent a ton of boxing
return (target instanceof Long) && Longs.indexOf(array, (Long) target, start, end) != -1;
}
@Override
public int indexOf(Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Long) {
int i = Longs.indexOf(array, (Long) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override
public int lastIndexOf(Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Long) {
int i = Longs.lastIndexOf(array, (Long) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override
public Long set(int index, Long element) {
checkElementIndex(index, size());
long oldValue = array[start + index];
// checkNotNull for GWT (do not optimize)
array[start + index] = checkNotNull(element);
return oldValue;
}
@Override
public List<Long> subList(int fromIndex, int toIndex) {
int size = size();
checkPositionIndexes(fromIndex, toIndex, size);
if (fromIndex == toIndex) {
return Collections.emptyList();
}
return new LongArrayAsList(array, start + fromIndex, start + toIndex);
}
@Override
public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (object instanceof LongArrayAsList) {
LongArrayAsList that = (LongArrayAsList) object;
int size = size();
if (that.size() != size) {
return false;
}
for (int i = 0; i < size; i++) {
if (array[start + i] != that.array[that.start + i]) {
return false;
}
}
return true;
}
return super.equals(object);
}
@Override
public int hashCode() {
int result = 1;
for (int i = start; i < end; i++) {
result = 31 * result + Longs.hashCode(array[i]);
}
return result;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder(size() * 10);
builder.append('[').append(array[start]);
for (int i = start + 1; i < end; i++) {
builder.append(", ").append(array[i]);
}
return builder.append(']').toString();
}
long[] toLongArray() {
// Arrays.copyOfRange() is not available under GWT
int size = size();
long[] result = new long[size];
System.arraycopy(array, start, result, 0, size);
return result;
}
private static final long serialVersionUID = 0;
}
}
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