數組

數組複製的方法

1. for循環複製

2. Arrays.copyOf(original, newLength);

   源數組 新數組長度

   int[] srcArray = {1,2,3,4,5,6};

   int[] newArray = Arrays.copyOf(srcArray, 10);

   // [1, 2, 3, 4, 5, 6, 0, 0, 0, 0]

   新長度大於源數組時，顯示爲類型初始化的值。int->0 String->null

3. System.arraycopy(src, srcPos, dest, destPos, length);

   源數組 | 起始索引|目標數組|起始位置|長度

   int[] srcArray = {1,2,3,4,5,6};

   int[] newArray = new int[srcArray.length];

   System.arraycopy(srcArray, 1, newArray, 0, 3);

   [2, 3, 4, 0, 0, 0]

   Arrays.copyOf 的底層實現也是通過System.arraycopy

       public static char[] copyOf(char[] original, int newLength) {

       char[] copy = new char[newLength];

       System.arraycopy(original, 0, copy, 0,

                        Math.min(original.length, newLength));

       return copy;

   }

ARRAYS工具類

• Arrays.toString(int[] a)

  ​int[] scores = { 3, 4, 7, 12, 43, 5,10, 6,1 };

  ​String s = Arrays.toString(scores);//數組轉字符串表達

  ​System.out.println(s);

  ​//將輸出：[3, 4,7, 12, 43, 5, 10, 6, 1]

• Arrays.sort(int[] a)

  ​Arrays.sort(scores);//對scores數組升序排列

• Arrays.fill(scores,5);

  ​int[] scores = { 3, 4, 7, 12, 43, 5,10, 6,1 };

  ​Arrays.fill(scores, 5);//將數組的所有值 替換成  5

  ​System.out.println(Arrays.toString(scores));

  ​//將輸出：[5, 5,5, 5, 5, 5, 5, 5, 5]