千锋逆战班学习第二十四天

千锋逆战班
在千锋"逆战”学习第24天,
每个人生阶段都需要努力去扮好自己的角色,越努力越轻松,越坚强越幸运!
加油!

1(Object类)有下面代码

interface IA{
	void ma();
}
class MyClass implements IA{
	public void ma() {}
	public String toString() {
		return "MyClass toString";
	}
}
public class Test11 {
	public static void main(String[] args) {
		IA ia=new MyClass();
		System.out.println(ia);
	}
}

結果為 MyClass toString

2

( StringBuilder )给定一个长度,随机产生一个该长度的字符串 ,由大写,小写字母以及数字组成。
Java中随机数的生成:
java.util.Random r = new java.util.Random();
int a = r.nextInt(100): a 0-99的随机数
提示:生成int值,并将int值转换成ASCII编码对应一个字符。

import java.util.Random;
import java.util.Scanner;
public class Test12 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		 char[] c=new char[3];
		StringBuilder s=new StringBuilder();
		Random r=new Random();
		Scanner sc=new Scanner(System.in);
		int i=sc.nextInt();
		for(int j=0;j<i;j++) {
			c[0]=(char) (r.nextInt(10)+48);
			c[1]=(char) (r.nextInt(26)+65);
			c[2]=(char) (r.nextInt(26)+97);
			s.append(c[r.nextInt(3)]);
		}
		System.out.println(s.toString());
	}

}

20
Ie7lO6RQ6lRCIe1AwMC7

3( String )给定-一个字符串,判断该字符串中是否包含某个子串.如果包含,求出子串的所有出现位置。

如: "abcd23abc34bcd"中, "bc"子串的出现位置为: 1,7,11.字符串和子串均由用户输入。

import java.util.Scanner;

public class Test13 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc=new Scanner(System.in);
		System.out.println("输入主字符串");
		String s1=sc.next();
		System.out.println("输入子字符串");
		String s2=sc.next();
		String[] s3=s1.split(s2);
		StringBuffer sb = new StringBuffer();
		int index = -1;
		for(int i = 0;i < s1.length();i++) {
			index = s1.indexOf(s2, index+1);
			if(index == -1) {
				break;	
			}
			else {
				sb.append(index+",");
			}
		}
		if(sb.length()==0) {
			System.out.println("不包含子字符串");
		}else{
			System.out.println("出現位置為"+sb.toString());
		}
		
	}
}

输入主字符串
dsahasiohf
输入子字符串
dhf
不包含子字符串
输入主字符串
hoioadhfhdiofhdasj
输入子字符串
fh
出現位置為7,12,

4

import java.util.ArrayList;
import java.util.List;
class Student{
	private String name;
	public Student() {}
	public Student(String name, int age, double score, String classString) {
		this.name = name;
		this.age = age;
		this.score = score;
		this.classString = classString;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public double getScore() {
		return score;
	}
	public void setScore(double score) {
		this.score = score;
	}
	public String getClassString() {
		return classString;
	}
	public void setClassString(String classString) {
		this.classString = classString;
	}
	private int age;
	private double score;
	private String classString;
}
public class Test14 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		List<Student> list = new ArrayList<Student>();
		list.add(new Student( "Tom" , 18, 100,"classO5" ));
		list.add(new Student( "Ierry" ,22, 70,"class04" ));
		list.add(new Student( "Owen" , 25, 90,"class05" ));
		list.add(new Student( "Jim" , 30,80,"class05" ));
		list.add(new Student( "Steve" , 28, 66,"class06" ));
		list.add(new Student( "Kevin" , 24, 100,"class04" ));
		avgage(list);
		avgScore(list);
	}
	public static void avgage(List<Student> list) {
		int sum=0;
		int avg;
		for(int i=0;i<list.size();i++) {
			sum=sum+list.get(i).getAge();
		}
		avg=sum/list.size();
		System.out.println("平均年齡"+avg);
	}
	public static void avgScore(List<Student> list) {
		double sum=0;
		double avg;
		for(int i=0;i<list.size();i++) {
			sum=sum+list.get(i).getScore();
		}
		avg=sum/list.size();
		System.out.println("平均成績"+avg);
	}

}

平均年齡24
平均成績84.33333333333333