JAVA基础之题目练习

0x01

编写类A01，定义方法max，实现求某个double数组的最大值，并返回Homework01.java

public class Homework01 {public static void main(String[] args){double[] numbers = {534, 1,34, 90, 56.9, 23, 45, 103.981};A01 a01 = new A01();System.out.println("The max number is " + a01.max(numbers));;}
}class A01{public double max(double[] number){double maxnum = number[0];int i = 0;for(; i < number.length; i++){maxnum = maxnum > number[i] ? maxnum : number[i];}return maxnum;}
}The max number is 534.0

0x02

编写类A02，定义方法find，实现查找某字符串数组中的元素查找，并返回索引，如果找不到，返回-1。

public class Homework02 {public static void main(String[] args){String[] data = {"hello", "hi", "yes", "no"};String finddata = "yes";A02 a02 = new A02();int index = a02.find(data, finddata);if(index == -1){System.out.println("NoFind, the index is " + index);}else {System.out.println("Find, the index is " + index);}}
}class A02{public int find(String[] data, String finddata){int i = 0;for(; i < data.length; i++){if(data[i].equals(finddata)){return i;}}return -1;}
}Find, the index is 2

0x03

编写类Book，定义方法updatePrice，实现更改某本书的价格，具体：如果价格>150，则更改为150，如果价格>100，更改为100，否则不变。

public class Homework03 {public static void main(String[] args){book bo = new book("xiyouji", 102.4);bo.updatePrice();}
}class book{String name;double price;public book(String name, double price){this.name = name;this.price = price;}public void updatePrice(){if(price > 150){price = 150;}else if(price > 100){price = 100;}System.out.println("The book name is " + name + ";price is " + price);}
}The book name is xiyouji;price is 100.0

0x04

编写类A03，实现数组的复制功能copyArr，输入旧数组，返回一个新数组，元素和旧数组一样。

public class Homework04 {public static void main(String[] args){A03 a03 = new A03();int[] arrOld = {1,2,3,9,8,7};int[] arrNew = a03.copyArr(arrOld);for (int i = 0; i < arrNew.length; i++){System.out.print(arrNew[i]);}}
}class A03{public int[] copyArr(int[] arrOld){int[] arrNew = new int[arrOld.length];for(int i = 0; i < arrOld.length; i++){arrNew[i] = arrOld[i];}return arrNew;}
}123987

0x05

定义一个圆类Circle，定义属性：半径，提供显示圆周长功能的方法，提供显示圆面积的方法。

public class Homework05 {public static void main(String[] args){Circle circle = new Circle(3);System.out.println("The circle Perimeter is " + circle.CalcPerimeter());System.out.println("The circle Perimeter is " + circle.CalcArea());}
}class Circle{double radius;public Circle(double radius){this.radius = radius;}public double CalcPerimeter(){return 2 * Math.PI * radius;}public double CalcArea(){return Math.PI * radius * radius;}
}The circle Perimeter is 18.84955592153876
The circle Perimeter is 28.274333882308138

0x06

编程创建一个Calc计算类，在其中定义2个变量表示两个操作数，定义四个方法实现求和、差、乘、差、商(要求除数为0的话，要提示)并创建两个对象，分别测试。

public class Homework06 {public static void main(String[] args){Calc calc1 = new Calc(4.56, 234);System.out.println("Add result is: " + calc1.add());System.out.println("Sub result is: " + calc1.sub());System.out.println("Mul result is: " + calc1.mul());Double divres1 = calc1.div();if(divres1 != null){System.out.println("Div result is: " + calc1.div());}Calc calc2 = new Calc(4.56, 0);System.out.println("Add result is: " + calc2.add());System.out.println("Sub result is: " + calc2.sub());System.out.println("Mul result is: " + calc2.mul());Double divres2 = calc2.div();if(divres2 != null){System.out.println("Div result is: " + calc2.div());}}
}class Calc{double a, b;public Calc(double a, double b){this.a = a;this.b = b;}public double add(){return a + b;}public double mul(){return a * b;}public double sub(){return a -b;}public Double div(){if(b == 0){System.out.println("b can not be 0!");return null;}return a / b;}
}Add result is: 238.56
Sub result is: -229.44
Mul result is: 1067.04
Div result is: 0.019487179487179485
Add result is: 4.56
Sub result is: 4.56
Mul result is: 0.0
b can not be 0!

0x07

设计一个Doog类，有名字、颜色和年龄属性，定义输出方法show()显示其信息。并创建对象，进行测试。(this属性)

public class Homework07 {public static void main(String[] args){Doog doog = new Doog("xiao", "white", 2);doog.show();}
}class Doog{String name;String colors;int age;public Doog(String name, String colors, int age){this.name = name;this.colors = colors;this.age = age;}public void show(){System.out.println("The dog name is " + name);System.out.println("The dog color is " + colors);System.out.println("The dog age is " + age);}}The dog name is xiao
The dog color is white
The dog age is 2

0x08

定义music类，里面有音乐名name、音乐时长times属性，并有播放play功能和返回本身属性信息的功能方法getinfo。

public class Homework08 {public static void main(String[] args){music mus = new music("yyy", 3.03);mus.play();String info = mus.getinfo();System.out.println(info);}
}class music{String name;double times;public music(String name, double times){this.name = name;this.times = times;}public void play(){System.out.println("The music name is " + name);System.out.println("The music time is " + times);}public String getinfo(){return "The music name is " + name + " The music time is " + times;}
}The music name is yyy
The music time is 3.03
The music name is yyy The music time is 3.03

0x09

在测试方法中，调用method方法，代码如下，编译正确，试写出method方法的定义形式，调用语句为：
System.out.println(method(method(10.0,20.0),100));

double method(double a, double b){}

0x0A

创建一个Employee类，属性有(名字，性别，年龄，职位，薪水)，提供3个构造方法，可以初始化 (1)(姓名，性别，年龄，职位，薪水)，(2)(名字，性别，年龄) (3)(职位，薪水)，要求充分复用构造器。

public class Homework09 {public static void main(String[] args){}
}class Employee{String name, job;char sex;int age;double salary;public Employee(String name, char sex, int age, String job, double salary){this(name, sex, age);this.job = job;this.salary = salary;}public Employee(String name, char sex, int age){this.name = name;this.sex = sex;this.age = age;}public Employee(String job, double salary){this.job = job;this.salary =salary;}
}

0x0B

将对象作为参数传递给方法

定义一个Circle2类，包含一个double型的radius属性代表圆的半径，findArea()方法返回圆的面积。
定义一个类PassObject，在类中定义一个方法printAreas()，该方法的定义如下：

public void printAreas(Circle2 c, int times) //方法签名
在printAreas方法中打印输出1到times之间的每个整数半径值，以及对应的面积。例如，times为5，则输出半径为1，2，3，4，5，以及对应的圆面积。
在main方法中调用printAreas()方法，调用完毕后输出当前半径值。

public class Homework10 {public static void main(String[] args){Circle2 circle2 = new Circle2();PassObject passObject = new PassObject();passObject.printAreas(circle2, 3);}
}class Circle2{double radius;public double findArea(){return Math.PI * radius * radius;}public void setRadius(int radius){this.radius = radius;}
}class PassObject{public void printAreas(Circle2 c, int times){for(int i = 1; i <= times; i++){c.setRadius(i);double area = c.findArea();System.out.println("The radius is " + i);System.out.println("The area is " + area);}}
}The radius is 1
The area is 3.141592653589793
The radius is 2
The area is 12.566370614359172
The radius is 3
The area is 28.274333882308138

0x0C

有个人Tom，设计他的成员变量，成员方法，可以电脑猜拳。
电脑每次都会随机生成0，1，2.
0表示石头，1表示剪刀，2表示布。
并要可以显示Tom的输赢次数。

public class Homework11 {public static void main(String[] args){Tom tom = new Tom(0);int times = tom.play();if(times <= 0){System.out.println("Tom wins 0 times");}else {System.out.println("Tom wins " + times + " times");}}
}class Tom{int res, times = 0;public Tom(int res){this.res = res;}public int play(){for(int i = 0; i < 100; i++){int comnum = (int)(Math.random() * 3);System.out.println("The computer is " + comnum);System.out.println("The Tom is " + res);if(res ==1 && comnum == 2){times += 1;}else if(res == 0 && comnum == 1){times += 1;}else if(res == 2 && comnum == 0){times += 1;}else if(res == comnum){times += 0;}else {times -= 1;}}return times;}
}

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JAVA基础之题目练习

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