关于Java中数组的常用操作方法

1. 声明一个数组

 String[] arr1 = new String[5];
 String[] arr2 = {"a","b","c", "d", "e"};
 String[] arr3= new String[]{"a","b","c","d","e"};  

2. 输出一个数组

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

 // 直接输出，为内存地址
 System.out.println(arr);
 // [I@139a55

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

3. 检查一个数组是否包含某值

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

4. 连接两个数组

 //使用Apache Commons Lang library

 1 int[] arr1 = { 1, 2, 3, 4, 5 };
 2 int[] arr2= { 6, 7, 8, 9, 10 };
 3 int[] combArr = ArrayUtils.addAll(arr1 , arr2); 

// System.arraycopy()
1 static String[] concat(String[] a, String[] b) {
       String[] c = new String[a.length + b.length];
       System.arraycopy(a, 0, c, 0, a.length);
       System.arraycopy(b, 0, c, a.length, b.length);
       return c;
  }

 //Arrays.copyOf()

 public static int[] concat(int[] first, int[] second) {
     int[] result = Arrays.copyOf(first, first.length + second.length);
     System.arraycopy(second, 0, result, first.length, second.length);
     return result;
 }

5. 逆向输出一个数组

 // Apache Commons Lang library

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

 int[] arr = { 1, 2, 3, 4, 5 };
 int[] revArr = new int[arr.length];
 for(int i = 0; i < arr.length; i++){
     revArr[i] = arr[arr.length - i -1];
 }
 System.out.println(Arrays.toString(revArr));

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

6. 移除数组中的元素

 // Apache common lang  

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