Arrays&Math

1、数组工具类Arrays
/*
* tostring()
* sort()
* */

public static void main(String[] args) {

    int [] array = {12,413,3};
    String str = java.util.Arrays.toString(array);
    System.out.println(str);


    java.util.Arrays.sort(array);
    System.out.println(java.util.Arrays.toString(array));


}

2、练习题

屏幕快照 2018-10-11 下午12.14.16.png

    public static void main(String[] args) {
    String str = "dfgdsdkasiuytqwrds";
    char [] charArr = str.toCharArray();

    System.out.println(Arrays.toString(charArr));
    //[d, f, g, d, s, d, k, a, s, i, u, y, t, q, w, r, d, s]

    Arrays.sort(charArr);
    System.out.println(Arrays.toString(charArr));
    //[a, d, d, d, d, f, g, i, k, q, r, s, s, s, t, u, w, y]

    //反向输出
    //ywutsssrqkigfdddda
    for (int i = 0; i < charArr.length; i++) {
        char cha = charArr[charArr.length-1-i];
        System.out.print(cha);
    }

}

二、Math

    public static void main(String[] args) {

    System.out.println(Math.abs(3.45));//绝对值
    System.out.println(Math.ceil(3.45));//向上取整
    System.out.println(Math.floor(3.45));//向下取整
    System.out.println(Math.round(3.45));//四舍五入

}