java.util.Arrays
基本信息
java.util.Arraysrt.jar- 引入版本：
JDK1.2
公共方法
靜態方法
| 靜態方法 |
|---|
void sort(int[] a)void sort(int[] a, int fromIndex, int toIndex)void sort(long[] a)void sort(long[] a, int fromIndex, int toIndex)void sort(short[] a)void sort(short[] a, int fromIndex, int toIndex)void sort(char[] a)void sort(char[] a, int fromIndex, int toIndex)void sort(byte[] a)void sort(byte[] a, int fromIndex, int toIndex)void sort(float[] a)void sort(float[] a, int fromIndex, int toIndex)void sort(double[] a)void sort(double[] a, int fromIndex, int toIndex)void sort(Object[] a)void sort(Object[] a, int fromIndex, int toIndex)<T> void sort(T[] a, Comparator<? super T> c)<T> void sort(T[] a, int fromIndex, int toIndex, Comparator<? super T> c)範圍排序時包前不報後，後索引取值最大爲數組長度值 |
void parallelSort(byte[] a)void parallelSort(byte[] a, int fromIndex, int toIndex)void parallelSort(char[] a)void parallelSort(char[] a, int fromIndex, int toIndex)void parallelSort(short[] a)void parallelSort(short[] a, int fromIndex, int toIndex)void parallelSort(int[] a)void parallelSort(int[] a, int fromIndex, int toIndex)void parallelSort(long[] a)void parallelSort(long[] a, int fromIndex, int toIndex)void parallelSort(float[] a)void parallelSort(float[] a, int fromIndex, int toIndex)void parallelSort(double[] a)void parallelSort(double[] a, int fromIndex, int toIndex)<T extends Comparable<? super T>> void parallelSort(T[] a)<T extends Comparable<? super T>> void parallelSort(T[] a, int fromIndex, int toIndex)<T> void parallelSort(T[] a, Comparator<? super T> cmp)<T> void parallelSort(T[] a, int fromIndex, int toIndex, Comparator<? super T> cmp)並行排序 |
<T> void parallelPrefix(T[] array, BinaryOperator<T> op)<T> void parallelPrefix(T[] array, int fromIndex, int toIndex, BinaryOperator<T> op)void parallelPrefix(long[] array, LongBinaryOperator op)void parallelPrefix(long[] array, int fromIndex, int toIndex, LongBinaryOperator op)void parallelPrefix(double[] array, DoubleBinaryOperator op)void parallelPrefix(double[] array, int fromIndex, int toIndex, DoubleBinaryOperator op)void parallelPrefix(int[] array, IntBinaryOperator op)void parallelPrefix(int[] array, int fromIndex, int toIndex, IntBinaryOperator op)執行累積方法，第一位和第二位作爲左右兩個值執行二元方法得到的值作爲左與第三位作爲右繼續執行 |
int binarySearch(long[] a, long key)int binarySearch(long[] a, int fromIndex, int toIndex, long key)int binarySearch(int[] a, int key)int binarySearch(int[] a, int fromIndex, int toIndex, int key)int binarySearch(short[] a, short key)int binarySearch(short[] a, int fromIndex, int toIndex, short key)int binarySearch(char[] a, char key)int binarySearch(char[] a, int fromIndex, int toIndex, char key)int binarySearch(byte[] a, byte key)int binarySearch(byte[] a, int fromIndex, int toIndex, byte key)int binarySearch(double[] a, double key)int binarySearch(double[] a, int fromIndex, int toIndex, double key)int binarySearch(float[] a, float key)int binarySearch(float[] a, int fromIndex, int toIndex, float key)int binarySearch(Object[] a, Object key)int binarySearch(Object[] a, int fromIndex, int toIndex, Object key)<T> int binarySearch(T[] a, T key, Comparator<? super T> c)<T> int binarySearch(T[] a, int fromIndex, int toIndex, T key, Comparator<? super T> c)需要數組已排序 如果數組包含多個具有指定值的元素，則無法保證找到哪個元素 當且僅當找到鍵時返回值 >=0 |
boolean equals(long[] a, long[] a2)boolean equals(int[] a, int[] a2)boolean equals(short[] a, short a2[])boolean equals(char[] a, char[] a2)boolean equals(byte[] a, byte[] a2)boolean equals(boolean[] a, boolean[] a2)boolean equals(double[] a, double[] a2)boolean equals(float[] a, float[] a2)boolean equals(Object[] a, Object[] a2)數組相等比較，對象數組時通過 equals 方法比較 |
boolean deepEquals(Object[] a1, Object[] a2)此方法適用於任意深度的 嵌套數組 |
void fill(long[] a, long val)void fill(long[] a, int fromIndex, int toIndex, long val)void fill(int[] a, int val)void fill(int[] a, int fromIndex, int toIndex, int val)void fill(short[] a, short val)void fill(short[] a, int fromIndex, int toIndex, short val)void fill(char[] a, char val)void fill(char[] a, int fromIndex, int toIndex, char val)void fill(byte[] a, byte val)void fill(byte[] a, int fromIndex, int toIndex, byte val)void fill(boolean[] a, boolean val)void fill(boolean[] a, int fromIndex, int toIndex, boolean val)void fill(double[] a, double val)void fill(double[] a, int fromIndex, int toIndex,double val)void fill(float[] a, float val)void fill(float[] a, int fromIndex, int toIndex, float val)void fill(Object[] a, Object val)void fill(Object[] a, int fromIndex, int toIndex, Object val)向數組內填充值，如果數組內已有值，則被覆蓋 |
byte[] copyOf(byte[] original, int newLength)short[] copyOf(short[] original, int newLength)int[] copyOf(int[] original, int newLength)long[] copyOf(long[] original, int newLength)char[] copyOf(char[] original, int newLength)float[] copyOf(float[] original, int newLength)double[] copyOf(double[] original, int newLength)boolean[] copyOf(boolean[] original, int newLength)<T> T[] copyOf(T[] original, int newLength)<T,U> T[] copyOf(U[] original, int newLength, Class<? extends T[]> newType)複製數組值到新的數組中，如果長度大於原數組長度，則大於原數組長度的部分爲初始值 |
<T> T[] copyOfRange(T[] original, int from, int to)<T,U> T[] copyOfRange(U[] original, int from, int to, Class<? extends T[]> newType)byte[] copyOfRange(byte[] original, int from, int to)short[] copyOfRange(short[] original, int from, int to)int[] copyOfRange(int[] original, int from, int to)long[] copyOfRange(long[] original, int from, int to)char[] copyOfRange(char[] original, int from, int to)float[] copyOfRange(float[] original, int from, int to)double[] copyOfRange(double[] original, int from, int to)boolean[] copyOfRange(boolean[] original, int from, int to)將指定數組的指定範圍複製到新數組中，包前不報後，如果 from == to ，返回空數組 |
<T> List<T> asList(T... a)返回由指定數組支持的固定大小的列表。 與 Collection.toArray 結合使用，此方法充當基於數組的 API 和基於集合的 API 之間的橋樑。 返回的實際上是 ArrayList。注意基本類型和對象的區別： List<int[]> intsList = Arrays.asList(ints);List<String> strList = Arrays.asList(strs); |
int hashCode(long a[])int hashCode(int a[])int hashCode(short a[])int hashCode(char a[])int hashCode(byte a[])int hashCode(boolean a[])int hashCode(float a[])int hashCode(double a[])int hashCode(Object a[])返回對象的哈希碼值。支持此方法是爲了使哈希表受益，例如 java.util.HashMap 提供的哈希表。 |
int deepHashCode(Object a[])根據指定數組的“深層內容”返回哈希碼。 |
String toString(long a[])String toString(int a[])String toString(short a[])String toString(char a[])String toString(byte a[])String toString(boolean a[])String toString(float a[])String toString(double a[])String toString(Object a[])更美觀的數組 toString 描述 |
String deepToString(Object[] a)支持多維數組 |
<T> void setAll(T[] array, IntFunction<? extends T> generator)void setAll(int[] array, IntUnaryOperator generator)void setAll(long[] array, IntToLongFunction generator)void setAll(double[] array, IntToDoubleFunction generator)使用提供的生成器函數來計算每個元素，設置指定數組的所有元素，生成器接受索引 併爲該位置產生所需值的函數 |
<T> void parallelSetAll(T[] array, IntFunction<? extends T> generator)void parallelSetAll(int[] array, IntUnaryOperator generator)void parallelSetAll(long[] array, IntToLongFunction generator)void parallelSetAll(double[] array, IntToDoubleFunction generator)並行執行 |
<T> Spliterator<T> spliterator(T[] array)<T> Spliterator<T> spliterator(T[] array, int startInclusive, int endExclusive)Spliterator.OfInt spliterator(int[] array)Spliterator.OfInt spliterator(int[] array, int startInclusive, int endExclusive)Spliterator.OfLong spliterator(long[] array)Spliterator.OfLong spliterator(long[] array, int startInclusive, int endExclusive)Spliterator.OfDouble spliterator(double[] array)Spliterator.OfDouble spliterator(double[] array, int startInclusive, int endExclusive)返回一個 Spliterator 對象 |
<T> Stream<T> stream(T[] array)<T> Stream<T> stream(T[] array, int startInclusive, int endExclusive)IntStream stream(int[] array)IntStream stream(int[] array, int startInclusive, int endExclusive)LongStream stream(long[] array)LongStream stream(long[] array, int startInclusive, int endExclusive)DoubleStream stream(double[] array)DoubleStream stream(double[] array, int startInclusive, int endExclusive)返回一個 Stream 對象 |
示例代碼
@Test
public void test() {
int[] ints = {2, 5, 4, 3, 1};
System.out.println("int[] ints 原數組 :: " + Arrays.toString(ints)); // int[] ints 原數組 :: [2, 5, 4, 3, 1]
int[] newInts = Arrays.copyOf(ints, ints.length);
Arrays.sort(newInts);
System.out.println("sort(int[] a) :: " + Arrays.toString(newInts)); // sort(int[] a) :: [1, 2, 3, 4, 5]
int[] newInts2 = Arrays.copyOf(ints, ints.length);
Arrays.sort(newInts2, 1, 4);
System.out.println("sort(int[] a, int fromIndex, int toIndex) :: " + Arrays.toString(newInts2)); // // sort(int[] a, int fromIndex, int toIndex) :: [2, 3, 4, 5, 1]
int[] newInts3 = Arrays.copyOf(ints, ints.length);
Arrays.parallelSort(newInts3);
System.out.println("parallelSort(int[] a) :: " + Arrays.toString(newInts3)); // parallelSort(int[] a) :: [1, 2, 3, 4, 5]
int[] newInts4 = Arrays.copyOf(ints, ints.length);
Arrays.parallelPrefix(newInts4, (left, right) -> left + right);
System.out.println("parallelPrefix(int[] array, IntBinaryOperator op) :: " + Arrays.toString(newInts4)); // parallelPrefix(int[] array, IntBinaryOperator op) :: [2, 7, 11, 14, 15]
int i = Arrays.binarySearch(newInts, 8);
System.out.println("binarySearch(int[] a, int key) :: " + i); // binarySearch(int[] a, int key) :: -6
boolean equals = Arrays.equals(ints, new int[]{2, 5, 4, 3, 1});
System.out.println("equals(int[] a, int[] a2) :: " + equals); // equals(int[] a, int[] a2) :: true
boolean b = Arrays.deepEquals(new int[][]{ints, ints}, new int[][]{ints, ints});
System.out.println("deepEquals(Object[] a1, Object[] a2) :: " + b); // deepEquals(Object[] a1, Object[] a2) :: true
int[] newInts5 = new int[10];
Arrays.fill(newInts5, 1);
System.out.println("fill(int[] a, int val) :: " + Arrays.toString(newInts5)); // fill(int[] a, int val) :: [1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
int[] newInts6 = new int[10];
Arrays.fill(newInts6, 1, 10, 2);
System.out.println("fill(int[] a, int val) :: " + Arrays.toString(newInts6)); // fill(int[] a, int val) :: [0, 2, 2, 2, 2, 2, 2, 2, 2, 2]
int[] newInts7 = Arrays.copyOf(ints, 3);
System.out.println("copyOf(int[] original, int newLength) :: " + Arrays.toString(newInts7)); // copyOf(int[] original, int newLength) :: [2, 5, 4]
int[] newInts8 = Arrays.copyOf(ints, 8);
System.out.println("copyOf(int[] original, int newLength) :: " + Arrays.toString(newInts8)); // copyOf(int[] original, int newLength) :: [2, 5, 4, 3, 1, 0, 0, 0]
int[] newInts9 = Arrays.copyOfRange(ints, 1, 1);
System.out.println("copyOfRange(int[] original, int from, int to) :: " + Arrays.toString(newInts9)); // copyOfRange(int[] original, int from, int to) :: [5, 4]
String[] strs = {"2", "5", "4", "3", "1"};
List<int[]> intsList = Arrays.asList(ints);
List<String> strList = Arrays.asList(strs);
System.out.println("asList(T... a) :: " + intsList); // asList(T... a) :: [[I@2f333739]
System.out.println("asList(T... a) :: " + strList); // asList(T... a) :: [2, 5, 4, 3, 1]
System.out.println("hashCode(int a[]) :: " + Arrays.hashCode(ints)); // hashCode(int a[]) :: 30629086
System.out.println("deepToString(Object[] a) :: " + Arrays.deepToString(new int[][]{ints, newInts2})); // deepToString(Object[] a) :: [[2, 5, 4, 3, 1], [2, 3, 4, 5, 1]]
int[] newInts10 = Arrays.copyOf(ints, ints.length);
Arrays.setAll(newInts10, o -> newInts10[o] * newInts10[o]);
System.out.println("setAll(int[] array, IntUnaryOperator generator) :: " + Arrays.toString(newInts10)); // setAll(int[] array, IntUnaryOperator generator) :: [4, 25, 16, 9, 1]
int[] newInts11 = Arrays.copyOf(ints, ints.length);
Arrays.parallelSetAll(newInts11, o -> newInts11[o] * newInts11[o]);
System.out.println("parallelSetAll(int[] array, IntUnaryOperator generator) :: " + Arrays.toString(newInts11)); // parallelSetAll(int[] array, IntUnaryOperator generator) :: [4, 25, 16, 9, 1]
Spliterator.OfInt spliterator = Arrays.spliterator(ints);
IntStream stream = Arrays.stream(ints);
System.out.println("原數組：" + Arrays.toString(ints)); // 原數組：[2, 5, 4, 3, 1]
}