ArrayUtils 工具類

ArrayUtils 是 Apache Commons Lang 3 工具包中常用的工具類，使用是需要依賴對應的lab,對應的maven引用如下：

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.5</version>
</dependency>

ArrayUtils提供了處理是數組的一些常用方法，包含基本類型數組，對象數組。做了一些非常漂亮的處理，來避免空值及其他類型的異常。

常用方法有
isEmpty 判斷數組是否為空
toString 按數組對象輸出
clone 拷貝
isNotEmpty 判斷數組是否不為空
toPrimitive 包裝類型數組轉換成基本類型數組（Integer 包裝類 --> int 基本類型）
indexOf 在數組中的下標
toObject 基本類型數組轉換成對應包裝類型數組
toMap 轉換成Map （數組元素是 key:value成對對象）
add 和addAll 添加單個元素或添加一個數組中的所有元素
remove 和 removeAll 刪除單個元素或刪除一個數組中所有元素
removeElement 和 removeElements 刪除第一個給的元素和刪除第一個給的數組
removeAllOccurences 刪除可能存在的元素（數組中可能有該元素也可能沒有）
contains 是否包含元素
reverse 反轉數組
shift 隨機打亂數組
subarray 獲取子數組
swap 交互數組指定位置元素

部分參考代碼

package org.kodejava.example.commons.lang;

import org.apache.commons.lang3.ArrayUtils;

public class PrimitiveArrayClone {
    public static void main(String[] args) {
        int[] fibonacci = new int[] {1, 1, 2, 3, 5, 8, 13, 21, 34, 55};
        System.out.println("fibonacci = " + ArrayUtils.toString(fibonacci));

        int[] clone = ArrayUtils.clone(fibonacci);
        System.out.println("clone = " + ArrayUtils.toString(clone));
    }
}


package org.kodejava.example.commons.lang;

import org.apache.commons.lang3.ArrayUtils;

public class ArrayUtilsToString {
    public static void main(String[] args) {
        // Print int array as string.
        int[] numbers = {1, 2, 3, 5, 8, 13, 21, 34};
        System.out.println("Numbers = " + ArrayUtils.toString(numbers));

        // Print string array as string.
        String[] grades = {"A", "B", "C", "D", "E", "F"};
        System.out.println("Grades = " + ArrayUtils.toString(grades));

        // Print multidimensional array as string.
        int[][] matrix = {{0, 1, 2}, {1, 2, 3}, {2, 3, 4}};
        System.out.println("Matrix = " + ArrayUtils.toString(matrix));

        // Return "Empty" when the array is null.
        String[] colors = null;
        System.out.println("Colors = " + ArrayUtils.toString(colors, "None"));
    }
}

Numbers = {1,2,3,5,8,13,21,34}
Grades = {A,B,C,D,E,F}
Matrix = {{0,1,2},{1,2,3},{2,3,4}}
Colors = None

package org.kodejava.example.commons.lang;

import org.apache.commons.lang3.ArrayUtils;

public class ArrayUtilsIndexOfDemo {
    public static void main(String[] args) {
        String[] colours = { "Red", "Orange", "Yellow", "Green",
            "Blue", "Violet", "Orange", "Blue" };

        // Does colours array contains the Blue colour?
        boolean contains = ArrayUtils.contains(colours, "Blue");
        System.out.println("Contains Blue? " + contains);

        // Can you tell me the index of each colour defined bellow?
        int indexOfYellow = ArrayUtils.indexOf(colours, "Yellow");
        System.out.println("indexOfYellow = " + indexOfYellow);

        int indexOfOrange = ArrayUtils.indexOf(colours, "Orange");
        System.out.println("indexOfOrange = " + indexOfOrange);

        int lastIndexOfOrange = ArrayUtils.lastIndexOf(colours, "Orange");
        System.out.println("lastIndexOfOrange = " + lastIndexOfOrange);
    }
}

package org.kodejava.example.commons.lang;

import org.apache.commons.lang3.ArrayUtils;

public class ArrayObjectToPrimitiveDemo {
    public static void main(String[] args) {
        // An array of Integer objects.
        Integer[] integers = {1, 2, 3, 5, 8, 13, 21, 34, 55};
        Boolean[] booleans = {Boolean.TRUE, Boolean.TRUE, Boolean.FALSE, Boolean.FALSE};

        // Convert array of Integer objects into array of type int.
        int[] ints = ArrayUtils.toPrimitive(integers);
        System.out.println(ArrayUtils.toString(ints));

        // Convert array of Boolean objects into array of type boolean.
        boolean[] bools = ArrayUtils.toPrimitive(booleans);
        System.out.println(ArrayUtils.toString(bools));
    }
}

package org.kodejava.example.commons.lang;

import java.util.Map;

import org.apache.commons.lang3.ArrayUtils;

public class ArrayToMapExample {

    public static void main(String[] args) {
        // A two dimensional array of countries capital.
        String[][] countries = {{"United States", "Washington, D.C."},
            {"United Kingdom", "London"},
            {"Netherlands", "Amsterdam"},
            {"Japan", "Tokyo"},
            {"France", "Paris"}};

        // Convert an array to a Map.
        Map capitals = ArrayUtils.toMap(countries);

        for (Object key : capitals.keySet()) {
            System.out.printf("%s is the capital of %s.%n", capitals.get(key), key);
        }
    }
}

package org.kodejava.example.commons.lang;

import org.apache.commons.lang3.ArrayUtils;

public class ArrayReverseExample {

    public static void main(String[] args) {
        // Define colors array.
        String[] colors = {"Red", "Green", "Blue", "Cyan", "Yellow", "Magenta"};
        System.out.println(ArrayUtils.toString(colors));

        // Now we reverse the order of array elements.
        ArrayUtils.reverse(colors);
        System.out.println(ArrayUtils.toString(colors));
    }
}

ackage org.kodejava.example.commons.lang;

import org.apache.commons.lang3.ArrayUtils;

public class ArrayPrimitiveObjectConversionDemo {
    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5};
        boolean[] booleans = {true, false, false, true};
        float[] decimals = {10.1f, 3.14f, 2.17f};

        Integer[] numbersObjects = ArrayUtils.toObject(numbers);
        Boolean[] booleansObjects = ArrayUtils.toObject(booleans);
        Float[] decimalsObjects = ArrayUtils.toObject(decimals);

        numbers = ArrayUtils.toPrimitive(numbersObjects);
        booleans = ArrayUtils.toPrimitive(booleansObjects);
        decimals = ArrayUtils.toPrimitive(decimalsObjects);
    }
}

int[] oldArray = { 2, 3, 4, 5 };
int[] newArray = ArrayUtils.add(oldArray, 0, 1);
int[] expectedArray = { 1, 2, 3, 4, 5 };
assertArrayEquals(expectedArray, newArray);


int[] oldArray = { 0, 1, 2 };
int[] newArray = ArrayUtils.addAll(oldArray, 3, 4, 5);
int[] expectedArray = { 0, 1, 2, 3, 4, 5 };
 
assertArrayEquals(expectedArray, newArray);

int[] oldArray = { 1, 2, 2, 2, 3 };
int[] newArray = ArrayUtils.removeAllOccurences(oldArray, 2);
int[] expectedArray = { 1, 3 };
 
assertArrayEquals(expectedArray, newArray);

int[] originalArray = { 1, 2, 3, 4, 5 };
ArrayUtils.reverse(originalArray);
int[] expectedArray = { 5, 4, 3, 2, 1 };
 
assertArrayEquals(expectedArray, originalArray);


int[] originalArray = { 1, 2, 3, 4, 5 };
ArrayUtils.shift(originalArray, 1);
int[] expectedArray = { 5, 1, 2, 3, 4 };
 
assertArrayEquals(expectedArray, originalArray);


int[] oldArray = { 1, 2, 3, 4, 5 };
int[] newArray = ArrayUtils.subarray(oldArray, 2, 7);
int[] expectedArray = { 3, 4, 5 };
 
assertArrayEquals(expectedArray, newArray);

int[] originalArray = { 1, 2, 3, 4, 5 };
ArrayUtils.swap(originalArray, 0, 3);
int[] expectedArray = { 4, 2, 3, 1, 5 };
assertArrayEquals(expectedArray, originalArray);

參考：
https://kodejava.org/tag/arrayutils/
https://www.codota.com/code/java/classes/org.apache.commons.lang.ArrayUtils
https://www.baeldung.com/array-processing-commons-lang
https://blog.csdn.net/yaomingyang/article/details/79127362
https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/ArrayUtils.html

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