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