Arrays类的十大用法

时间：2022-11-09 14:39:04

还有很多地方需要细细斟酌

0. 声明数组

 String[] aArray = new String[5];

 String[] bArray = {"a","b","c", "d", "e"};

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

1. 打印数组

 int[] intArray = { 1, 2, 3, 4, 5 };

 String intArrayString = Arrays.toString(intArray);  

 // 直接打印,则会打印出引用对象的Hash值

 // [I@7150bd4d

 System.out.println(intArray);  

 // [1, 2, 3, 4, 5]

 System.out.println(intArrayString);

2. 根据数组创建ArrayList

 String[] stringArray = { "a", "b", "c", "d", "e" };

 ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));

 // [a, b, c, d, e]

 System.out.println(arrayList);

3. 检查数组是否包含某个值

 String[] stringArray = { "a", "b", "c", "d", "e" };

 boolean b = Arrays.asList(stringArray).contains("a");

 // true

 System.out.println(b);

4. 合并连接两个数组

 int[] intArray = { 1, 2, 3, 4, 5 };

 int[] intArray2 = { 6, 7, 8, 9, 10 };

 // Apache Commons Lang 库

 int[] combinedIntArray = ArrayUtils.addAll(intArray, intArray2);

5. 声明内联数组

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

6. 用给定的字符串连结(join)数组

 // containing the provided list of elements

 // Apache common lang

 String j = StringUtils.join(new String[] { "a", "b", "c" }, ", ");

 // a, b, c

 System.out.println(j);

7. 将ArrayList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);

8. 将数组转换为Set

 Set<String> set = new HashSet<String>(Arrays.asList(stringArray));

 //[d, e, b, c, a]

 System.out.println(set)

9. 数组元素反转

 int[] intArray = { 1, 2, 3, 4, 5 };

 ArrayUtils.reverse(intArray);

 //[5, 4, 3, 2, 1]

 System.out.println(Arrays.toString(intArray));

10. 移除元素

 int[] intArray = { 1, 2, 3, 4, 5 };

 int[] removed = ArrayUtils.removeElement(intArray, 3);//创建新的数组

 System.out.println(Arrays.toString(removed));

更多——转换int值为字节数组

 byte[] bytes = ByteBuffer.allocate(4).putInt(8).array();  

 for (byte t : bytes) {

    System.out.format("0x%x ", t);

 }

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