java数组10大技巧

0.  声明一个数组（Declare an array）

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

1.  在Java中输出一个数组（Print an array in Java）

 int[] intArray = { 1, 2, 3, 4, 5 };
 String intArrayString = Arrays.toString(intArray);  

 // print directly will print reference value
 System.out.println(intArray);
 // [I@7150bd4d  

 System.out.println(intArrayString);
 // [1, 2, 3, 4, 5] 

2. 从数组中创建数组列表（Create an ArrayList from an array）

 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]  

3. 检查数组中是否包含特定值（Check if an array contains a certain value）

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

4. 连接两个数组（ Concatenate two arrays）

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

5. 声明一个数组内链（Declare an array inline ）

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

6. 将数组元素加入到一个独立的字符串中（Joins the elements of the provided array into a single String）

 // 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  

7. 将数组列表转换成一个数组 （Covnert an ArrayList to an array）

 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. 将数组转换成一个集合（Convert an array to a set）

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

9. 反向数组（Reverse an array）

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

10. 删除数组元素（Remove element of an array）

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

One more – convert int to byte array

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

 for (byte t : bytes) {
    System.out.format("0x%x ", t);
 }