EduCoder Java程序设计---Java面向对象（五）- 常用类_package case1; import java.util.scanner; public cl

第1关 Object类

package case1;
 
import java.util.Scanner;
 
public class ObjectTest {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int num1 = sc.nextInt();
		int num2 = sc.nextInt();
		// ÔÚ²âÊÔÀàÖд´½¨DemoÀà¶ÔÏód1£¬´«ÈëÊäÈëÖµnum1£¬ d1µ÷ÓÃtoString·½·¨²¢´òÓ¡Êä³ö¸ÃÖµ
		// ´´½¨DemoÀà¶ÔÏód2£¬Í¬Ñù´«ÈëÊäÈëÖµnum1£¬´òÓ¡ÅжÏd1ºÍd2ÊÇ·ñÏàµÈ£¨Êµ¼ÊÊDZȽϵØÖ·£©
		/********* Begin *********/
		Demo d1 = new Demo(num1);
		System.out.println(d1.toString());
		Demo d2 = new Demo(num1);
		System.out.println(d1.equals(d2));
		/********* End *********/
		// ´´½¨PersonÀà¶ÔÏóp£¬´«ÈëÊäÈëÖµnum2£¬´òÓ¡ÅжÏd1ºÍpÊÇ·ñÏàµÈ£¨Êµ¼ÊÊDZȽϵØÖ·£©
		/********* Begin *********/
		Person p = new Person(num2);
		System.out.println(d1.equals(p));
		/********* End *********/
	}
}
 
class Demo {
	private int num;
 
	public Demo(int num) {
		this.num = num;
	}
 
	public boolean equals(Object obj) // Object obj = new Demo()
	{
		if (!(obj instanceof Demo)) // ÅжÏobjÊÇ·ñºÍDemoÊÇͬÀà
			return false;
		Demo d = (Demo) obj; // ½«¸¸ÀàµÄÒýÓÃ(Object)ÏòÏÂת»»Îª×ÓÀà(Demo)
		return this.num == d.num;
	}
 
	public String toString() {
		return "Demo:" + num; // ·µ»Ø¶ÔÏóµÄÖµ£¨Ã¿Ò»¸ö¶ÔÏó¶¼ÓÐ×Ô¼ºµÄÌض¨µÄ×Ö·û´®£©
	}
}
 
class Person {
	private int num;
 
	public Person(int num) {
		this.num = num;
	}
}

第2关 JAVA基础类型包装类-练习

package case2;
 
import java.util.Scanner;
 
public class WrapperTest {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int aa = sc.nextInt();
		String bb = sc.next();
		int c = sc.nextInt();
		String str11 = sc.next();
		String str22 = sc.next();
		// °ü×°ÀàÖС°==¡±ÓëequalsµÄÓ÷¨±È½Ï
		// ÖµµÃ×¢ÒâµÄÊÇ£¬°ü×°ÀàÖеÄequals·½·¨ºÍStringÀàÒ»Ñù£¬¶¼ÊÇÖØдÁËObjectÀàÖеÄequals·½·¨£¬Òò´Ë±È½ÏµÄÊÇÄÚÈݶø²»ÊǵØÖ·£¬
		// ¶ø¡°==¡±±È½ÏµÄÒÀÈ»ÊÇÒýÓñäÁ¿µÄµØÖ·£¬Ö»Êǵ±°ü×°ÀàÐͺÍÓëÖ®Ïà¶ÔÓ¦µÄ»ù±¾ÀàÐͽøÐС°==¡±±È½Ïʱ»áÏÈ×ö×Ô¶¯²ðÏä´¦Àí¡£
		/********* Begin *********/
		Integer a = aa;
		Integer b = new Integer(bb);
		String str1 = str11;
		String str2 = str22;
		System.out.println(a==b);
		System.out.println(a==c);
		System.out.println(b==c);
		System.out.println(a.equals(b));
		System.out.println(str1==str2);
		System.out.println(str1.equals(str2));
		/********* End *********/
	}
}

第3关 String&StringBuilder&StringBuffer类-练习

package case3;
 
import java.util.Scanner;
 
public class StringTest {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		// String substring(int start,int end)
		// ½ØÈ¡×Ö·û´®£¬´«ÈëµÄÁ½¸ö²ÎÊý·Ö±ðΪҪ½ØÈ¡±ß½çµÄϱê
		// ÔÚjava api ÖÐ,ͨ³£Ê¹ÓÃÁ½¸öÊý×Ö±íʾ·¶Î§Ê±,¶¼ÊǺ¬Í·²»º¬Î²,¼´°üº¬Æðʼϱê¶ÔÓ¦µÄÄÚÈÝ,µ«²»°üº¬½áÊøϱêµÄ´¦¶ÔÓ¦µÄÄÚÈÝ
		// String toUpperCase() ½«µ±Ç°×Ö·û´®ÖеÄÓ¢ÎIJ¿·Öת»»ÎªÈ«´óд
		/********* Begin *********/
 
		String str1 = str.substring(12,str.lastIndexOf("."));
		if(str1.indexOf(".")>0){
			str1 = str1.substring(0,str1.indexOf("."));
		}
		System.out.println(str1);
		System.out.println(str1.toUpperCase());
		/********* End *********/
	}
}

第4关 Random类

package case4;
 
//ÃÜÂëµÄ×Ô¶¯Éú³ÉÆ÷£ºÃÜÂëÓÉ´óд×Öĸ/Сд×Öĸ/Êý×Ö×é³É£¬Éú³ÉÁùλËæ»úÃÜÂë
import java.util.Random;
import java.util.Scanner;
 
public class RandomTest {
	public static void main(String[] args) {
		// ¶¨ÒåÒ»¸ö×Ö·ûÐÍÊý×é
		char[] pardStore = new char[62];
		// °ÑËùÓеĴóд×Öĸ·Å½øÈ¥ °ÑËùÓеÄСд×Öĸ·Å½øÈ¥ °Ñ0µ½9·Å½øÈ¥
		/********* Begin *********/
		for (int i = 0 ; i < 26 ; i++){
			pardStore[i] = (char)('A' + i );
			pardStore[26+i] = (char)('a'+i);
		}
		for(int i = 0 ; i <10 ; i ++ ){
			pardStore[52+i] = (char)('0'+i);
		}
		/********* End *********/
		// ·Ö±ðÒÔ1¡¢2¡¢3×÷ΪÖÖ×ÓÊý Éú³É6λËæ»úÃÜÂë
		Scanner sc = new Scanner(System.in);
		int seed = sc.nextInt();
		/********* Begin *********/
		Random random = new Random(seed);
		String str = "";
		int [] arr = random.ints(6,0,62).toArray();
		for( int i = 0 ; i < 6 ; i ++  ){
			str += pardStore[arr[i]];
 
		}
		System.out.println(str);
		/********* End *********/
	}
}

第5关 Date类和SimpleDateFormat类的用法

package case5;
 
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;
 
public class DateTest {
	public static void main(String[] args) throws ParseException {
		// ¼üÅ̼ÈëÄãµÄ³öÉúÄêÔÂÈÕ ¸ñʽΪyyyy-MM-dd
		// °Ñ¸Ã×Ö·û´®×ª»»ÎªÒ»¸öÈÕÆÚ
		// ͨ¹ý¸ÃÈÕÆڵõ½Ò»¸öºÁÃëÖµ
		// »ñÈ¡2020Äê10ÔÂ1ÈյĺÁÃëÖµ
		// Á½ÕßÏë¼õµÃµ½Ò»¸öºÁÃëÖµ
		// °Ñ¸ÃºÁÃëֵת»»ÎªÌì ´òÓ¡Êä³ö
		Scanner sc = new Scanner(System.in);
		String line = sc.nextLine();
		/********* Begin *********/
		SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
		Date d1 = sf.parse(line);
		Date d2 = sf.parse("2020-10-01");
		long diff = d2.getTime()-d1.getTime();
		diff = diff/86400000;
		System.out.println("你的出生日期距离2020年10月1日:"+diff+"天");
 
 
 
		/********* End *********/
	}
}

第6关 Math类

package case6;
 
import java.util.Scanner;
import java.lang.Math;
 
public class MathTest {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a1 = sc.nextInt();
		int a2 = sc.nextInt();
		int a3 = sc.nextInt();
		int a4 = sc.nextInt();
		double a5 = sc.nextDouble();
		double a6 = sc.nextDouble();
		double a7 = sc.nextDouble();
		double a8 = sc.nextDouble();
		double a9 = sc.nextDouble();
		double a10 = sc.nextDouble();
		double a11 = sc.nextDouble();
		/********* Begin *********/
		System.out.println(Math.sqrt(a1));
		System.out.println(Math.cbrt(a2));
		System.out.println(Math.pow(a3,a4));
		System.out.println(Math.max(a5,a6));
		System.out.println(Math.min(a5,a6));
		System.out.println(Math.abs(a7));
		System.out.println(Math.ceil(a8));
		System.out.println(Math.floor(a9));
		System.out.println(Math.rint(a10));
		System.out.println(Math.round(a11));
		/********* End *********/
	}
}