Java_部分杂七杂八的方法

小插曲

package cn.Alan_DS;
import java.util.Random;
/**
 * @author 15328
 * 随机给出0-12之间的数字，并显示对应月份
 */
public class ThirdFirst {
    public static void showString(int x) {
        switch (x) {
            case 1:
                System.out.println(x + " = Jan");
                break;
            case 2:
                System.out.println(x + " = Feb");
                break;
            case 3:
                System.out.println(x + " = Mar");
                break;
            case 4:
                System.out.println(x + " = Apr");
                break;
            case 5:
                System.out.println(x + " = May");
                break;
            case 6:
                System.out.println(x + " = Jun");
                break;
            case 7:
                System.out.println(x + " = Jul");
                break;
            case 8:
                System.out.println(x + " = Aug");
                break;
            case 9:
                System.out.println(x + " = Sep");
                break;
            case 10:
                System.out.println(x + " = Oct");
                break;
            case 11:
                System.out.println(x + " = Nov");
                break;
            case 12:
                System.out.println(x + " = Dec");
                break;
            default:
                System.out.println("out of 0-12 ");
        }
    }

    public static void main(String[] args) {
        int randX;
        int x = 24;
        while(x > 0) {
            RandProduce randExample = new RandProduce();
            randX = randExample.x;
            showString(randX + 1);
            x--;
        }
    }
}
class RandProduce {
    Random rand = new Random();
    int x = rand.nextInt(12);
}

package cn.Alan_DS;

/**
 * @author 15328
 */
public class MathMethod {
    public static void main(String[] args) {
        TrigonmetricMethod x1 = new TrigonmetricMethod();
        ExponentMethod x2 = new ExponentMethod();
        SeriveceMethod x3 = new SeriveceMethod();
        x1.showMethod();
        x2.showMethod();
        x3.showIntMethod();
        x3.showOthers();
    }
}
class TrigonmetricMethod{
    /**三角函数方法*/
    public void showMethod(){
        System.out.println(Math.toDegrees(Math.PI / 2)); //弧度转为角度 //返回值为角度的数值
        System.out.println(Math.toRadians(90.0));//角度转为弧度 //返回值为弧度的数值
        System.out.printf("%.2f\n",Math.sin(Math.PI / 6.0));//返回以弧度制为单位的正弦值
        System.out.printf("%.2f\n",Math.cos(Math.PI / 3.0));//返回值为弧度的数值
        System.out.println(Math.asin(0.5));//返回值为弧度的数值
        System.out.println(Math.acos(0.5));//返回值为弧度的数值
        System.out.println(Math.atan(1.0));//返回值为弧度的数值
    }
}
class ExponentMethod{
    /**指数函数方法*/
    public void showMethod(){
        System.out.println(Math.exp(3.5));//e^3.5
        System.out.println(Math.log(3.5));//ln(3.5)
        System.out.println(Math.log10(3.5));//log10(3.5)
        System.out.println(Math.pow(4,10));//4^10
        System.out.println(Math.sqrt(3.5));//根号3.5
    }
}
class SeriveceMethod{
    public void showIntMethod(){
        System.out.println(Math.ceil(2.1));//向上取整
        System.out.println(Math.floor(2.1));//向下取整
        System.out.println(Math.rint(2.6));//返回最接近的整数，距离相等则返回偶数数值
        System.out.println(Math.round(2.8));//x为floor,返回(int)Math.floor(x+0.5);  x为double，返回(long)Math.floor(x+0.5);
    }
    public void showOthers(){
        System.out.println(Math.min(4,12));
        System.out.println(Math.max(15,22));
        System.out.println(Math.abs(-55));//返回绝对值
        System.out.println(Math.random());//0.0 <= Math.random() < 1.0 的double数值
    }
}

package cn.Alan_DS;

import java.util.Locale;

/**
 * @author 15328
 */
public class StringMethod {
    public static void main(String[] args) {
        CharMethod ch1 = new CharMethod();
        ch1.showCharMethod();
        ch1.showStringMethod();
        ch1.toMath();
    }
}
class CharMethod{
    String x = "java\\jdk16";
    String t = "12345";
    String s = "123.789";
    String y = "java//jdk8.0.3";
    public void showCharMethod(){
        System.out.println(Character.isDigit('5'));//指定字符是数字，返回TRUE
        System.out.println(Character.isLetter('k'));//指定字符是字母，返回TRUE
        System.out.println(Character.isUpperCase('p'));//是大写字母
        System.out.println(Character.isLetterOrDigit('4'));//是字母或者数字
        System.out.println(Character.isLowerCase('o'));//是小写字母
    }
    public void showStringMethod(){
        System.out.println(x.length());
        System.out.println(x.charAt(5));//返回字符串中指定位置的字符
        System.out.println(x.concat(y));//将x与y连接，返回一个新的字符串
        System.out.println(x.toLowerCase());//返回一个新字符串，所有字母小写
        System.out.println(x.toUpperCase());//返回一个新字符串，所有字母小写
        System.out.println(x.equals(y));
        System.out.println(x.equalsIgnoreCase(y));//无论大小写比较大小
        System.out.println(x.compareTo(y));//返回一个大于0、等于零、小于0的整数，表明字符串x是否大于等于小于y
        System.out.println(x.startsWith("java"));//是否以特定前缀开始
        System.out.println(x.endsWith("jdk16"));//是否以特定后缀结束
        System.out.println(x.contains("dk"));//是否包含此子串
        System.out.println(x.substring(5));//返回从指定位置字符到字符串结尾的子串
        System.out.println(x.substring(2,6));//返回从beginIndex位置到endIndex-1位置的字符串
        System.out.println(x.indexOf('a'));//返回第一个出现ch字符的下标，如果没有返回-1
        System.out.println(x.indexOf("jdk"));
        System.out.println(x.indexOf("jdk",2));//fromIndex位置之后出现第一个该子串的下标
        System.out.println(x.indexOf('j',5));//返回fromIndex位置以及它之后出现的第一个ch的下标
        System.out.println(x.lastIndexOf('j'));
    }
    public void toMath(){
        System.out.println(Integer.parseInt(t));
        System.out.println(Double.parseDouble(s)+Integer.parseInt(t));
    }
}

package cn.Alan_DS;

import java.util.Arrays;
/**
 * @author 15328
 * 可变长参数列表
 * Arrays类
 */
public class ArrayMethod {
    public static void main(String[] args) {
        printMax(34,3,3,2,56.5);
        printMax(new double[]{1, 22.6, 8});
        arraysMethod(new double[]{1,2,5,55.9,99.112,333.568,0.456789});
    }
    public static void printMax(double...numbers){
        /**可变长参数列表*/
        if(numbers.length == 0){
            System.out.println("No arguments passed");
            return;
        }
        double result = numbers[0];
        for(int i = 1; i < numbers.length; i++) {
            if(numbers[i]>result){
                result = numbers[i];
            }
        }
        System.out.println("The Max value is " + result);
    }
    public static void arraysMethod(double [] list){
        /**Arrays类*/
        Arrays.sort(list);
        System.out.println(Arrays.toString(list));
        Arrays.sort(new double[]{12,26.8,99.0},1,3);//fromindex到toindex-1的位置下标进行排序
        System.out.println(Arrays.binarySearch(list,12));
        //对已经排好序的数组进行二分查找，找key的值，找到返回下标，
        // 找不到，返回-(应该插入的位置下标+1）
        System.out.println(Arrays.equals(list,new double[]{11.0,12.5,99.99}));
        Arrays.fill(list,10);//fill 10 to the whole array
        System.out.println(Arrays.toString(list));
        Arrays.fill(list,1,5,8);//fill 1-4, with the 8
        System.out.println(Arrays.toString(list));
    }
}