forked from fanruan/easyexcel
Jiaju Zhuang
4 years ago
6 changed files with 154 additions and 50 deletions
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package com.alibaba.excel.util; |
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import java.util.ArrayList; |
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import java.util.List; |
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/** |
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* Int utils |
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* |
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* @author Jiaju Zhuang |
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**/ |
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public class IntUtils { |
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private IntUtils() {} |
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/** |
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* Returns the {@code int} nearest in value to {@code value}. |
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* |
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* @param value any {@code long} value |
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* @return the same value cast to {@code int} if it is in the range of the {@code int} type, |
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* {@link Integer#MAX_VALUE} if it is too large, or {@link Integer#MIN_VALUE} if it is too |
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* small |
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*/ |
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public static int saturatedCast(long value) { |
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if (value > Integer.MAX_VALUE) { |
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return Integer.MAX_VALUE; |
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} |
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if (value < Integer.MIN_VALUE) { |
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return Integer.MIN_VALUE; |
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} |
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return (int) value; |
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} |
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} |
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@ -0,0 +1,63 @@
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package com.alibaba.excel.util; |
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import java.util.ArrayList; |
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import java.util.List; |
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/** |
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* List utils |
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* |
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* @author Jiaju Zhuang |
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**/ |
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public class ListUtils { |
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private ListUtils() {} |
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/** |
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* Creates an {@code ArrayList} instance backed by an array with the specified initial size; |
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* simply delegates to {@link ArrayList#ArrayList(int)}. |
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* |
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* <p><b>Note for Java 7 and later:</b> this method is now unnecessary and should be treated as |
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* deprecated. Instead, use {@code new }{@link ArrayList#ArrayList(int) ArrayList}{@code <>(int)} |
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* directly, taking advantage of the new <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>. |
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* (Unlike here, there is no risk of overload ambiguity, since the {@code ArrayList} constructors |
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* very wisely did not accept varargs.) |
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* |
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* @param initialArraySize the exact size of the initial backing array for the returned array list |
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* ({@code ArrayList} documentation calls this value the "capacity") |
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* @return a new, empty {@code ArrayList} which is guaranteed not to resize itself unless its size |
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* reaches {@code initialArraySize + 1} |
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* @throws IllegalArgumentException if {@code initialArraySize} is negative |
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*/ |
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public static <E> ArrayList<E> newArrayListWithCapacity(int initialArraySize) { |
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checkNonnegative(initialArraySize, "initialArraySize"); |
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return new ArrayList<>(initialArraySize); |
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} |
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/** |
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* Creates an {@code ArrayList} instance to hold {@code estimatedSize} elements, <i>plus</i> an |
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* unspecified amount of padding; you almost certainly mean to call {@link |
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* #newArrayListWithCapacity} (see that method for further advice on usage). |
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* |
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* <p><b>Note:</b> This method will soon be deprecated. Even in the rare case that you do want |
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* some amount of padding, it's best if you choose your desired amount explicitly. |
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* |
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* @param estimatedSize an estimate of the eventual {@link List#size()} of the new list |
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* @return a new, empty {@code ArrayList}, sized appropriately to hold the estimated number of |
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* elements |
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* @throws IllegalArgumentException if {@code estimatedSize} is negative |
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*/ |
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public static <E> ArrayList<E> newArrayListWithExpectedSize(int estimatedSize) { |
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return new ArrayList<>(computeArrayListCapacity(estimatedSize)); |
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} |
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static int computeArrayListCapacity(int arraySize) { |
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checkNonnegative(arraySize, "arraySize"); |
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return IntUtils.saturatedCast(5L + arraySize + (arraySize / 10)); |
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} |
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static int checkNonnegative(int value, String name) { |
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if (value < 0) { |
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throw new IllegalArgumentException(name + " cannot be negative but was: " + value); |
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} |
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return value; |
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} |
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} |
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