java--Arrays

1、toString

将数组拼接成字符串

public class arrays {
   
    public static void main(String[] args) {
   
        int[] arr = {
   11,33,22,55,44};
        System.out.println(Arrays.toString(arr));
    }
}

2、binarySearch

用二分查找法查找元素

返回的是索引，如果不存在返回 负插入点减1

public class arrays {
   
    public static void main(String[] args) {
   
        int[] arr = {
   11,22,33,44,55};
        int i = Arrays.binarySearch(arr, 22);
        System.out.println(i);
    }
}

3、copyof

拷贝数组

• 新数组长度小于老数组，会部分拷贝
• 新数组长度大于老数组，会全部拷贝，再补上默认值
• 新数组长度等于老数组，会完全拷贝

public class arrays {
   
    public static void main(String[] args) {
   
        int[] arr = {
   11,22,33,44,55};
        int[] ints = Arrays.copyOf(arr, 2);
        for (int i = 0; i < ints.length; i++) {
   
            System.out.println(ints[i]);
        }
    }
}

4、copyOfRange

指定拷贝数组

public class arrays {
   
    public static void main(String[] args) {
   
        int[] arr = {
   11,22,33,44,55};
        int[] ints = Arrays.copyOfRange(arr,0,4);
        for (int i = 0; i < ints.length; i++) {
   
            System.out.println(ints[i]);
        }
    }
}

5、fill

填充数组

将所有值填充为100

public class arrays {
   
    public static void main(String[] args) {
   
        int[] arr = new int[10];
        Arrays.fill(arr,100);
        for (int i = 0; i < arr.length; i++) {
   
            System.out.println(arr[i]);
        }
    }
}

6、sort

排序数组

默认情况下用升序，算法用的是快速排序

public class arrays {
   
    public static void main(String[] args) {
   
        int[] arr = {
   11,33,54,22};
        Arrays.sort(arr);
        for (int i = 0; i < arr.length; i++) {
   
            System.out.println(arr[i]);
        }
    }
}