The common methods of Arrays tools are briefly described as follows:
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Arrays.equals(a1,a2): Determine whether the two arrays a1 and a2 are equal, that is, whether each element is equal;
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Arrays.fill(a,val): fill the specified value val into the array a;
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dest = Arrays.copyOf(src,newLength): Assign the contents of the array src to the array dest, and the length of dest is newLength;
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Arrays.sort(a): Sort the internal elements of array a, sorting in ascending order by default.
To use the above method, you need to import the array tool import java.util.Arrays;
1.Arrays.equals方法
2.Arrays.fill method
For example, there are now 10 array variables of 99. It is obviously a burden to input repeated numbers, especially when there are many repeated numbers. Therefore, in order to solve this problem, the Arrays.fill method is used to optimize the following code:
......
// 构造一个包含十个99的数组变量
// int[] prices = {99, 99, 99, 99, 99, 99, 99, 99, 99, 99};
int[] prices = new int[10]; // 声明一个整型数组，数组大小为10
Arrays.fill(prices, 99); // 给整型数组的每个元素全部填写99
for (int price : prices) {
// 循环遍历并打印整型数组的所有元素数值
System.out.println("price = "+price);
3.Arrays.copyOf method
This method allows copying several (indeterminate) elements from the source array to the target array.
......
int[] pricesOrigin = {
99, 99, 99, 99, 99 }; // 声明一个整型数组，数组大小为5，且5个元素全为99
for (int price : pricesOrigin) {
System.out.println("origin price = " + price);
}
// 复制数组的第三个办法：调用Arrays工具的copyOf方法。允许复制部分元素
int[] pricesCopy = Arrays.copyOf(pricesOrigin, pricesOrigin.length);
for (int price : pricesCopy) {
// 循环遍历并打印整型数组的所有元素数值
System.out.println("copy price = " + price);
}
// 改变copyOf方法的第二个参数值，允许复制指定大小的数组元素
int[] pricesPart = Arrays.copyOf(pricesOrigin, pricesOrigin.length - 1);
for (int price : pricesPart) {
// 循环遍历并打印整型数组的所有元素数值
System.out.println("part price = " + price);
}
// 把copyOf方法的返回值赋给原数组，可以动态调整该数组的大小
pricesOrigin = Arrays.copyOf(pricesOrigin, pricesOrigin.length + 1);
for (int price : pricesOrigin) {
// 循环遍历并打印整型数组的所有元素数值
System.out.println("origin price = " + price);
}
4.Arrays.sort method
As the name implies, the sort method of the Arrays tool sorts the array elements, and the default sort result is ascending.
The following code is to generate a dynamic random array, involving arrays, loops, colon jumps and other techniques for sorting:
......
int[] numbers = new int[10]; // 创建一个大小为10的动态整型数组
loop: for (int i = 0; i < numbers.length; i++) {
int item = new Random().nextInt(100); // 生成一个小于100的随机整数
// 下面的循环用来检查数组中是否已经存在该随机数
for (int j = 0; j < i; j++) {
if (numbers[j] == item) {
// 已经存在该随机数，则继续第一层循环，重新生成随机数
i--; // 本次循环做了无用功，取消当前的计数
continue loop; // 继续以loop标记的外层循环
}
}
numbers[i] = item; // 原数组不存在该随机数，则把随机数加入到数组中
}
// 对整型数组numbers里的元素排序，sort方法得到的结果是升序排列
Arrays.sort(numbers);
for (int number : numbers) {
// 循环遍历并打印整型数组的所有随机数
System.out.println("number = " + number);
}
The sort method optimization code is behind