java的Arrays工具类

1年多了，jdk还不是很熟，补补。

package lhy.core.util;

import java.util.Arrays;
import java.util.List;

public class ArraysTest {
    public static void main(String[] args) {
        
        
        int[] aa = {2,1,3,15,12,6}; 
        
        //1,数组转换成字符串:toString(int[] a) 
        System.out.println(Arrays.toString(aa));//[1, 2, 3, 4, 5, 6]
        
        
        
        //2,复制指定的数组，截取或用 0 填充 copyOf(float[] original,int newLength)
        double[] dd = {4.1,6.2,3.4,9.6,8.8};
        double[] ddCopy = Arrays.copyOf(dd, 7);
        for (double d : ddCopy) {
            System.out.print(d + "  "); //4.1  6.2  3.4  9.6  8.8  0.0  0.0  
        }
        
        System.out.println("
复制数组指定范围到新数组：");
        //将指定数组的指定范围复制到一个新数组。
        int[] aaCopy = Arrays.copyOfRange(aa, 0, 3);
        for (int i : aaCopy) {
            System.out.print(i + "  ");//2  1  3  
        }
        
        
        
        System.out.println("
数组转list：");
        //3,数组转list
        String[] str = {"tom","jack","mashibing"};
        List<String> list = Arrays.asList(str);
        for (String string : list) {
            System.out.println(string);
        }
        
        
        System.out.println("快速排序sort:");
        //4,数组排序sort：快速排序
        Arrays.sort(aa);
        for (int a : aa) {
            System.out.print(a + "  "); //1  2  3  6  12  15  
        }
        System.out.println("
只排序数组指定下标部分：");
        //对指定下标部分 排序
        Arrays.sort(dd, 2, 4);
        for (double d : dd) {
            System.out.print(d +"  ");
        }
        
        
        
        System.out.println("
binarySearch二分查找：");
        //5：二分查找，必须先排序
        Arrays.sort(aa);
        int key = Arrays.binarySearch(aa, 4);
        if(key >= 0){//找到了key >= 0
            System.out.println("查找结果，key："+key+"  值为："+aa[key]);
        }else{
            System.out.println("数组中未查找到4，key:"+key); //数组中未查找到4，key:-4
        }
        //二分查找数组指定范围：
        key = Arrays.binarySearch(aa, 0, 3, 3);
        if(key >= 0){//找到了key >= 0
            System.out.println("查找结果，key："+key +" 值："+aa[key]); //查找结果，key：2 值：3
        }
        
        
        
        System.out.println("
替换数组的值：");
        //6：替换数组的值
        int[] arr = new int[5];
        Arrays.fill(arr, 2);
        for (int i : arr) {
            System.out.print(i+"  "); //2  2  2  2  2 
        }
        System.out.println("
部分替换数组的值：");
        Arrays.fill(arr, 1, 3, 5);
        for (int i : arr) {
            System.out.print(i + "  ");//2  5  5  2  2  
        }
        
        
        
        System.out.println("
挨着比较2个数组值是否相等：");
        //7：比较2个数组是否相等
        int[] arr1 = {1,2,3,4};
        int[] arr2 = {2,1,3,4};
        System.out.println(Arrays.equals(arr1, arr2)); //false
        
    }

    
}