Java练习（注意）

1.输入学生的姓名，将学生姓名按照字母顺序进行排序

注意：有问题

package com.jredu.ch09;

import java.util.Arrays;

import java.util.Scanner;

public class Order {

/**

* 获取排序之后的数组

* @return

*/

public String[] getSortArray() {

//排序前的数组

System.out.println("请输入五个学生姓名");

String[] stu=new String[5];

Scanner in=new Scanner(System.in);

for(int i=0;i<stu.length;i++) {

stu[i]=in.next();

}

//排序后的数组

Arrays.sort(stu);

return stu;

}

public static void main(String[] args) {

Order ch=new Order();

ch.getSortArray();

System.out.println("\t排序以后");

System.out.println("********************");

System.out.println(Arrays.toString(ch.getSortArray()));

}

}

2.n个人围成一圈，顺序排序，从第一个人开始报数，从1-3开始报数，凡报到三的人退出圈子， 问最后剩下的是原来第几号的那位

package com.jredu.ch09;

import java.util.Arrays;

import java.util.Scanner;

public class Round {

/**

* 2:2

* 3:2

* 4:1

* 5:4

* 7:4

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

//用数组存储数据

// int[] person={1,2,0,4,5,6,7};

// {1,2,0,4,5,6,7}3

// {1,2,0,4,5,0,7}6

// {1,0,0,4,5,0,7}2

// {1,0,0,4,5,0,0}7

// {1,0,0,4,0,0,0}5

// {0,0,0,4,0,0,0}1

System.out.print("请输入人数");

Scanner sc=new Scanner(System.in);

int count=sc.nextInt();

int[] person=new int[count];

for(int i=0;i<count;i++) {

person[i]=i+1;

}

int num=0;

int length=count;

for(int i=0;i<count;i++) {

// num++;

//如果num是3，

if(person[i]!=0) {

num++;

}

if(num==3) {

//并且当前数字不是0，就把当前数字变成0

if(person[i]!=0) {

// System.out.println(person[i]);

person[i]=0;

num=0;

length--;

// System.out.println(Arrays.toString(person));

// System.out.println(i+1);

} else {

continue;

}

}

if(i==count-1) {

i=-1;

}

if(length==1) {

for(int j:person) {

if(j!=0) {

System.out.println("最后剩下的是"+j);

}

}

return;

}

}

}

}

3.输入一个数字，插入到一个有序数组中，并排序

package com.jredu.ch09;

import java.util.Arrays;

import java.util.Scanner;

public class Sort {

public static void main(String[] args) {

int[] a={2,3,6,7,18};

Scanner in=new Scanner(System.in);

System.out.print("请输入数字");

int num=in.nextInt();

int[] b=Arrays.copyOf(a, a.length+1);

b[a.length]=num;

a=null;

a=b;

b=null;

Arrays.sort(a);

System.out.println(Arrays.toString(a));

}

}

4.创建两个类：以对象作为方法的参数进行传递

学生类：

package com.jredu.ch09;

public class Stu {

public int java;

public int c;

public int oracle;

public Stu(int java, int c, int oracle) {

super();

this.java = java;

this.c = c;

this.oracle = oracle;

}

}

学生服务类：

package com.jredu.ch09;

public class StuService {

public int getAvg(Stu stu) {

return (stu.java+stu.c+stu.oracle)/3;

}

public static void main(String[] args) {

Stu wm=new Stu(80, 80, 80);

Stu xgx=new Stu(85, 85, 85);

StuService service=new StuService();

// int a=10;

int avg=service.getAvg(wm);

int avg1=service.getAvg(xgx);

System.out.println("平均成绩是"+avg);

System.out.println("平均成绩是"+avg1);

}

}

5.

Student类：

package com.jredu.ch10;

/**

* 学生类

* @author Administrator

*

*/

public class Student {

public String name;

public int age;

public double height;

public Student(double height) {

super();

this.height = height;

}

}

StudentManager类

package com.jredu.ch10;

import java.util.Scanner;

public class StudentManager {

/**

* 计算学生平均身高

* @param array

* @return

*/

public double getHeightAvg(Student[] array) {

double sum=0;

for(Student stu:array) {

// stu.height 每个学生的身高

sum+=stu.height;

}

return sum/array.length;

}

public static void main(String[] args) {

//得到所有的学生

Student[] array=new Student[5];

Scanner in=new Scanner(System.in);

for(int i=0;i<array.length;i++) {

System.out.print("请输入第"+(i+1)+"个学生的身高(cm):");

//根据身高，定义学生对象

// Student stu=new Student(in.nextDouble());

array[i]=new Student(in.nextDouble());

}

StudentManager manager=new StudentManager();

double avg=manager.getHeightAvg(array);

System.out.println("***这"+array.length+"名学生的平均身高是:"+avg+"cm***");

}

}

HeightManager类

package com.jredu.ch10;

public class HeightManager {

/**

* 求平均值

* @param array

* @return

*/

public double avg(double[] array) {

int sum=0;

for(int i=0;i<array.length;i++) {

sum+=array[i];

}

return sum/array.length;

}

public double stuAvg(Student[] array) {

Student stu=array[0];

double sum=0;

for(int i=0;i<array.length;i++) {

sum+=array[i].height;

}

return sum/array.length;

}

public static void main(String[] args) {

double [] array={180,190,173,163,158};

// double a=180;

// Student stu=new Student(180);

String str="";

String str2=new String("");

Student [] arr2={new Student(180),new Student(180),

new Student(180),new Student(180),new Student(180)};

//求平均值

HeightManager manager=new HeightManager();

System.out.println("平均值是"+manager.avg(array));

}

}

6. 并且通过会员编号查找会员积分

Vip类

package com.jredu.ch09;

public class Vip {

public int num;

public int score;

public Vip() {

super();

this.num = num;

this.score = score;

}

public int getNum(){

return num;

}

public float getScore(){

return score;

}

}

VipOprate类

package com.jredu.ch09;

import java.util.Scanner;

public class VipOprate {

public void addVip(Vip[] vip) {

System.out.println("*****会员列表*****");

System.out.println("编号\t积分");

for(int i=0;i<vip.length;i++){

System.out.print("\n"+vip[i].num+"\t"+vip[i].score);

}

}

public int searchScore(Vip[] vip,int searchNum){

int newScore=0;

for(int i=0;i<vip.length;i++){

if(searchNum==vip[i].num){

newScore=vip[i].score;

break;

}

}

return newScore;

}

public static void main(String[] args) {

// TODO Auto-generated method stub

Scanner in = new Scanner(System.in);

Vip[] vip =new Vip[5];

VipOprate oprate = new VipOprate();

for(int i=0;i<vip.length;i++){

vip[i]=new Vip();

System.out.print("请输入会员编号：");

vip[i].num = in.nextInt();

System.out.print("请输入会员积分：");

vip[i].score = in.nextInt();

}

oprate.addVip(vip);

System.out.print("请输入要查找的编号：");

int n=in.nextInt();

int newScore=oprate.searchScore(vip, n);

System.out.println("该会员的积分为："+newScore);

}

}

老师讲的

user类

package com.jredu.ch10;

public class User {

public int no;//会员编号

public int score;//会员积分

public User(int no, int score) {

super();

this.no = no;

this.score = score;

}

}

usermanager类

package com.jredu.ch10;

import java.util.Scanner;

public class UserManager {

public User[] users=new User[100];//会员数组

public int index=0;

/**

* 添加会员

* @param user

*/

public void addUser(User user) {

users[index]=user;

index++;

}

public void show() {

System.out.println("***会员列表***");

System.out.println("编号\t积分");

for(User u:users) {

if(u!=null) {

//打印会员信息

System.out.println(u.no+"\t"+u.score);

} else {

break;

}

}

}

public User search(int no){

//遍历所有的会员信息，查找是否存在该用户

for(User u:users){

if(u.no==no){

//找到了

return u;

}

}

return null;

}

public static void main(String[] args) {

Scanner in=new Scanner(System.in);

UserManager manager=new UserManager();

while(true) {

System.out.print("请输入会员编号");

int no=in.nextInt();

if(no>0) {

System.out.print("请输入会员积分");

int score=in.nextInt();

// User user=new User(no,score);

manager.addUser(new User(no,score));

} else {

break;

}

}

manager.show();

//查找

System.out.print("请输入要查找的会员编号：");

User user=manager.search(in.nextInt());

if(user!=null){

System.out.println("该会员积分是："+user.score);

}else{

System.out.println("不存在该会员");

}

}

}