JavaSE:13、常用工具类

学习 资源1

学习资源 2

1、数学工具类

import com.test.*;

import java.util.Random;
import java.util.RandomAccess;

public class Main {
    public static  void main(String [] argv) throws Exception {
   System.out.println(Math.pow(5,3));//125.0
   System.out.println(Math.abs(-198.6));//198.6
   System.out.println(Math.min(7,90));//7
   System.out.println(Math.max(90,7));//90
   System.out.println(Math.sqrt(36));//6.0
   System.out.println(Math.sin(Math.PI/2));//1.0
   System.out.println(Math.tan(Math.PI/2));//1.633123935319537E16   有误差
   System.out.println(Math.log10(100));//2.0
   System.out.println(Math.log(Math.E));//1.0
   System.out.println(Math.ceil(4.6));//5.0
   System.out.println(Math.floor(4.5));//4.0
        Random random=new Random();
     System.out.println( random.nextInt(100));//98  随机数，再运行一次结果不一样

    }
}

2、数组工具类

import com.test.*;

import java.util.Arrays;


public class Main {
    public static  void main(String [] argv)  {
   int arr[]=new int[]{1,2,3,4,5,6,7,9,8};
   System.out.println(Arrays.toString(arr));
   //[1, 2, 3, 4, 5, 6, 7, 9, 8]
        Arrays.sort(arr);
   System.out.println(Arrays.toString(arr));
   //[1, 2, 3, 4, 5, 6, 7, 8, 9]
   int b[]=Arrays.copyOf(arr,5);
   System.out.println(Arrays.toString(b));
   //[1, 2, 3, 4, 5]
   int c[]=Arrays.copyOfRange(arr,2,5);
   System.out.println(Arrays.toString(c));
   //[3, 4, 5]
   int d[]=new int[10];
   System.arraycopy(arr,2,d,3,2);
   //[0, 0, 0, 3, 4, 0, 0, 0, 0, 0]
   System.out.println(Arrays.toString(d));
   //[0, 0, 0, 3, 4, 0, 0, 0, 0, 0]
   System.out.println(Arrays.binarySearch(arr,5));
   //4
   System.out.println(Arrays.equals(arr,c));
   //false
   Arrays.fill(arr,2);
   System.out.println(Arrays.toString(arr));
   //[2, 2, 2, 2, 2, 2, 2, 2, 2]

   int e[][]=new int[][]{{1,2},{2,3}};
   int f[][]=new int[][]{{1,2},{2,3}};
   System.out.println(Arrays.deepToString(e));
   //[[1, 2], [2, 3]]
   System.out.println(Arrays.deepEquals(e,f));
   //true
    }
}