数组常用

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" };


在Java中输出一个数组

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

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

System.out.println(intArrayString);
// [1, 2, 3, 4, 5] 从数组中创建数组列表

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] 检查数组中是否包含特定值

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

声明一个数组内链

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

将数组元素加入到一个独立的字符串中

// 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 将数组列表转换成一个数组

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);


将数组转换成一个集合

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

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

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

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);
}