数组

数组复制的方法

1. for循环复制

2. Arrays.copyOf(original, newLength);

   源数组 新数组长度

    
   int[] srcArray = {1,2,3,4,5,6};
   int[] newArray = Arrays.copyOf(srcArray, 10);
   // [1, 2, 3, 4, 5, 6, 0, 0, 0, 0]
   

   新长度大于源数组时，显示为类型初始化的值。int->0 String->null

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

   源数组 | 起始索引|目标数组|起始位置|长度

    
   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 的底层实现也是通过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工具类

• Arrays.toString(int[] a)

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

  ​String s = Arrays.toString(scores);//数组转字符串表达

  ​System.out.println(s);

  ​//将输出：[3, 4,7, 12, 43, 5, 10, 6, 1]

• Arrays.sort(int[] a)

  ​Arrays.sort(scores);//对scores数组升序排列

• Arrays.fill(scores,5);

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

  ​Arrays.fill(scores, 5);//将数组的所有值 替换成  5

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

  ​//将输出：[5, 5,5, 5, 5, 5, 5, 5, 5]