超实用的Java数组技巧攻略

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);
}