关于 Java 数组的 12 个最佳方法

Posted 2020-08-25 易小川

1.  声明一个数组

String[] aArray = new String[5];  
String[] bArray = {"a","b","c", "d", "e"};  
String[] cArray = new String[]{"a","b","c","d","e"}; 

2.  输出一个数组

    int[] intArray = { 1, 2, 3, 4, 5 };  
    String intArrayString = Arrays.toString(intArray);  
       
    // print directly will print reference value  
    System.out.println(intArray);  
    // [[email protected]  
       
    System.out.println(intArrayString);  
    // [1, 2, 3, 4, 5]  

3.  从一个数组创建数组列表

    String[] stringArray = { "a", "b", "c", "d", "e" };  
    ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));  
    System.out.println(arrayList);  
    // [a, b, c, d, e]  

4.  检查一个数组是否包含某个值

    String[] stringArray = { "a", "b", "c", "d", "e" };  
    boolean b = Arrays.asList(stringArray).contains("a");  
    System.out.println(b);  
    // true  

5.  连接两个数组

int[] intArray = { 1, 2, 3, 4, 5 };  
int[] intArray2 = { 6, 7, 8, 9, 10 };  
// Apache Commons Lang library  
int[] combinedIntArray = ArrayUtils.addAll(intArray, intArray2); 

6.  声明一个内联数组（Array inline）

method(new String[]{"a", "b", "c", "d", "e"}); 

7.  把提供的数组元素放入一个字符串

    // containing the provided list of elements  
    // Apache common lang  
    String j = StringUtils.join(new String[] { "a", "b", "c" }, ", ");  
    System.out.println(j);  
    // a, b, c  

8.  将一个数组列表转换为数组

    String[] stringArray = { "a", "b", "c", "d", "e" };  
    ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));  
    String[] stringArr = new String[arrayList.size()];  
    arrayList.toArray(stringArr);  
    for (String s : stringArr)  
        System.out.println(s);  

9.  将一个数组转换为集（set）

    Set<String> set = new HashSet<String>(Arrays.asList(stringArray));  
    System.out.println(set);  
    //[d, e, b, c, a]  

10.  逆向一个数组

    int[] intArray = { 1, 2, 3, 4, 5 };  
    ArrayUtils.reverse(intArray);  
    System.out.println(Arrays.toString(intArray));  
    //[5, 4, 3, 2, 1]  

11.  移除数组中的元素

    int[] intArray = { 1, 2, 3, 4, 5 };  
    int[] removed = ArrayUtils.removeElement(intArray, 3);//create a new array  
    System.out.println(Arrays.toString(removed));  

12.  将整数转换为字节数组

    byte[] bytes = ByteBuffer.allocate(4).putInt(8).array();  
       
    for (byte t : bytes) {  
       System.out.format("0x%x ", t);  
    }