Java程序与设计11

文章目录

11.01
- 实现思路
- Code
12.06
- 实现思路
- Code
12.08
- 实现思路
12.11
- 实现思路
- Code
11.01
- 实现思路
- Code
12.05
- 实现思路
- Code
12.06
- 实现思路
- Code
12.08
- 实现思路
12.11
- 实现思路
- Code
- 运行结果

11.01

实现思路

子类可以继承父类的方法,如果覆盖了则需要创建父类对象来调用(如父类的toString());在之类中可以用super调用父类的方法.

Code

import java.util.Scanner;class GeometricObject {private String color ="white";private boolean filled;private java.util.Date dateCreated;public GeometricObject(){dateCreated = new java.util.Date();}public GeometricObject(String color,boolean filled){dateCreated = new java.util.Date();this.color = color;this.filled = filled;}public String getColor(){return color;}public void setColor(String color){this.color = color;}public boolean isfilled(){return filled;}public void setFilled(boolean filled){this.filled = filled;}public java.util.Date getDateCreated(){return dateCreated;}public String toString(){return "created on " + dateCreated +"\ncolor: "+color+" and filled: "+filled;}
}
class Triangle extends GeometricObject{private double side1,side2,side3;public Triangle(){this("white", false ,1.0,1.0,1.0);}public Triangle(String color,boolean filled,double side1, double side2, double side3){super(color,filled);this.side1 = side1;this.side2 = side2;this.side3 = side3;}public double getSide1() {return side1;}public double getSide2() {return side2;}public double getSide3() {return side3;}public double getArea(){double p=this.getPerimeter()/2.0;return  Math.sqrt(p*(p-side1)*(p-side2)*(p-side3));}public double getPerimeter(){return side1+side2+side3;}public String toString(){return getClass().getName()+": side1="+side1+" side2="+side2+" side3="+side3;}
}
public class exercise_11_01{public static void main(String[] args){Scanner input = new Scanner(System.in);System.out.println("Please enter three sides respectively:");double side1 = input.nextDouble();double side2 = input.nextDouble();double side3 = input.nextDouble();System.out.println("Please enter the color of the triangle and if it is filled:");String color = input.next();boolean filled = input.nextBoolean();GeometricObject g = new GeometricObject(color, filled);Triangle triangle = new Triangle(color, filled,side1,side2,side3);System.out.println(g.toString());System.out.println(""+triangle);System.out.println("The area is "+triangle.getArea());System.out.println("The perimeter is "+triangle.getPerimeter());input.close();}
}

###运行结果

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##12.05
###实现思路
定义IllegalTriangleException然后声明异常并接住异常,需要注意的是声明是在方法签名"()"之后,"{}"之前: throws IllegalTriangleException
###Code

import java.util.Scanner;
class GeometricObject {private String color ="white";private boolean filled;private java.util.Date dateCreated;public GeometricObject(){dateCreated = new java.util.Date();}public GeometricObject(String color,boolean filled){dateCreated = new java.util.Date();this.color = color;this.filled = filled;}public String toString(){return "created on " + dateCreated +"\ncolor: "+color+" and filled: "+filled;}
}
class IllegalTriangleException extends Exception{/****/private static final long serialVersionUID = 1L;//private double side1, side2, side3;public IllegalTriangleException(double side1,double side2,double side3){super("Invalid side"+" "+ side1+" "+side2+" "+ side3);// this.side1=side1;// this.side2=side2;// this.side3=side3;}
}
class Triangle extends GeometricObject{private double side1,side2,side3;public Triangle() throws IllegalTriangleException {this("white", false ,1.0,1.0,1.0);}public Triangle(String color,boolean filled,double side1, double side2, double side3) throws IllegalTriangleException {super(color,filled);if(side1+side2>side3 && side1+side3>side2 && side2+side3>side1){this.side1 = side1;this.side2 = side2;this.side3 = side3;}elsethrow new IllegalTriangleException(side1,side2,side3);}public double getArea(){double p=this.getPerimeter()/2.0;return  Math.sqrt(p*(p-side1)*(p-side2)*(p-side3));}public double getPerimeter(){return side1+side2+side3;}public String toString(){return getClass().getName()+": side1="+side1+" side2="+side2+" side3="+side3;}
}
public class exercise_12_05{public static void main(String[] args){Scanner input = new Scanner(System.in);System.out.println("Please enter three sides respectively:");double side1 = input.nextDouble();double side2 = input.nextDouble();double side3 = input.nextDouble();System.out.println("Please enter the color of the triangle and if it is filled:");String color = input.next();boolean filled = input.nextBoolean();try{GeometricObject g = new GeometricObject(color, filled);Triangle triangle = new Triangle(color, filled,side1,side2,side3);System.out.println(g.toString());System.out.println(""+triangle);System.out.println("The area is "+triangle.getArea());System.out.println("The perimeter is "+triangle.getPerimeter());input.close();}catch (IllegalTriangleException ex){System.out.println(ex.getMessage());}}
}

12.06

实现思路

将字符串先转化为一个个字符,然后对字符通过减去ASCII起始码的操作转化为数字.最后将这些数字按照十六进制数的计数法则(每逢是16进一位)得到其十进制的数值.
NumberFormatException是已经有的异常,判断不是十六进制字符串的条件应当是其自身的每个字符是否符合了在0~1或A~F的输入表示法.

Code

import java.util.Scanner;
public class exercise_12_06{public static void main(String[] args){Scanner input = new Scanner(System.in);System.out.print("Please enter a hex number: ");try {String hex = input.nextLine();System.out.println("The decimal value for hex number " + hex+"is "+hexToDec(hex.toUpperCase()));input.close();} catch (NumberFormatException ex) {System.out.println(ex);}}public static int hexToDec(String hex) throws NumberFormatException {//十六进制字符串除了在开头用0x标志之外,本身它的构成也只可能是0~1与A~Fint hexcharToDecimal=0,decimalValue=0;for(int i=0;i<hex.length();i++){char ch = hex.charAt(i);if(ch>='A' && ch<='F'){hexcharToDecimal = 10+ ch - 'A';}else if(ch>='0' && ch<='9')hexcharToDecimal = ch - '0';else//异常本身也是一种方法,故而需要()throw new NumberFormatException();decimalValue = decimalValue * 16 + hexcharToDecimal;}return decimalValue;}}

12.08

实现思路

如果是NumberFormatException ex,ex即java.lang.NumberFormatException,ex.getMessage()无内容;对于自定义的异常类,ex为HexFormatException: HexFormatException,ex.getMessage()有内容即HexFormatException

12.11

实现思路

命令行读入文件名与需要的替换字符串,创建file对象,判断file.exists(),在构建器中读入文本用replaceAll()处理后,再写进原文档.
值得一提的是.replaceAll()方法不支持中文,如果是文章开头是中文,将会没有输出;如果文章中间是中文,会输出乱码. 此外,命令行似乎不接受"",想通过读入空字符串然后替代删除原文中字符串不可以,于是在源代码中replaceAll()写入"".

Code

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;
public class exercise_12_11 {public static void main(String[] args) throws FileNotFoundException {File sourceFile  = new File(args[1]);//判断文件是否存在if(!sourceFile.exists()){System.out.println("File don't exist.");}//创建一个空的字符串构建器,sb的对象为StringBuilder类Scanner input = new Scanner(sourceFile);StringBuilder sb = new StringBuilder();//在还有内容可以读的时候,不停地读入下一行while(input.hasNext()){String line = input.nextLine();//对windows而言,回车/r加换行/n才能真正换行sb.append(line.replaceAll(args[0],"")+"\r\n");}input.close();//再把内容从构建器中输出出来PrintWriter output = new PrintWriter(sourceFile);//必须使用toString()方法才可以将构建器中的字符序列输出给新的String类对象output.println(sb.toString());output.close();}
}

11.01

实现思路

子类可以继承父类的方法,如果覆盖了则需要创建父类对象来调用(如父类的toString());在之类中可以用super调用父类的方法.

Code

import java.util.Scanner;class GeometricObject {private String color ="white";private boolean filled;private java.util.Date dateCreated;public GeometricObject(){dateCreated = new java.util.Date();}public GeometricObject(String color,boolean filled){dateCreated = new java.util.Date();this.color = color;this.filled = filled;}public String getColor(){return color;}public void setColor(String color){this.color = color;}public boolean isfilled(){return filled;}public void setFilled(boolean filled){this.filled = filled;}public java.util.Date getDateCreated(){return dateCreated;}public String toString(){return "created on " + dateCreated +"\ncolor: "+color+" and filled: "+filled;}
}
class Triangle extends GeometricObject{private double side1,side2,side3;public Triangle(){this("white", false ,1.0,1.0,1.0);}public Triangle(String color,boolean filled,double side1, double side2, double side3){super(color,filled);this.side1 = side1;this.side2 = side2;this.side3 = side3;}public double getSide1() {return side1;}public double getSide2() {return side2;}public double getSide3() {return side3;}public double getArea(){double p=this.getPerimeter()/2.0;return  Math.sqrt(p*(p-side1)*(p-side2)*(p-side3));}public double getPerimeter(){return side1+side2+side3;}public String toString(){return getClass().getName()+": side1="+side1+" side2="+side2+" side3="+side3;}
}
public class exercise_11_01{public static void main(String[] args){Scanner input = new Scanner(System.in);System.out.println("Please enter three sides respectively:");double side1 = input.nextDouble();double side2 = input.nextDouble();double side3 = input.nextDouble();System.out.println("Please enter the color of the triangle and if it is filled:");String color = input.next();boolean filled = input.nextBoolean();GeometricObject g = new GeometricObject(color, filled);Triangle triangle = new Triangle(color, filled,side1,side2,side3);System.out.println(g.toString());System.out.println(""+triangle);System.out.println("The area is "+triangle.getArea());System.out.println("The perimeter is "+triangle.getPerimeter());input.close();}
}

12.05

实现思路

定义IllegalTriangleException然后声明异常并接住异常,需要注意的是声明是在方法签名"()"之后,"{}"之前: throws IllegalTriangleException

Code

import java.util.Scanner;
class GeometricObject {private String color ="white";private boolean filled;private java.util.Date dateCreated;public GeometricObject(){dateCreated = new java.util.Date();}public GeometricObject(String color,boolean filled){dateCreated = new java.util.Date();this.color = color;this.filled = filled;}public String toString(){return "created on " + dateCreated +"\ncolor: "+color+" and filled: "+filled;}
}
class IllegalTriangleException extends Exception{/****/private static final long serialVersionUID = 1L;//private double side1, side2, side3;public IllegalTriangleException(double side1,double side2,double side3){super("Invalid side"+" "+ side1+" "+side2+" "+ side3);// this.side1=side1;// this.side2=side2;// this.side3=side3;}
}
class Triangle extends GeometricObject{private double side1,side2,side3;public Triangle() throws IllegalTriangleException {this("white", false ,1.0,1.0,1.0);}public Triangle(String color,boolean filled,double side1, double side2, double side3) throws IllegalTriangleException {super(color,filled);if(side1+side2>side3 && side1+side3>side2 && side2+side3>side1){this.side1 = side1;this.side2 = side2;this.side3 = side3;}elsethrow new IllegalTriangleException(side1,side2,side3);}public double getArea(){double p=this.getPerimeter()/2.0;return  Math.sqrt(p*(p-side1)*(p-side2)*(p-side3));}public double getPerimeter(){return side1+side2+side3;}public String toString(){return getClass().getName()+": side1="+side1+" side2="+side2+" side3="+side3;}
}
public class exercise_12_05{public static void main(String[] args){Scanner input = new Scanner(System.in);System.out.println("Please enter three sides respectively:");double side1 = input.nextDouble();double side2 = input.nextDouble();double side3 = input.nextDouble();System.out.println("Please enter the color of the triangle and if it is filled:");String color = input.next();boolean filled = input.nextBoolean();try{GeometricObject g = new GeometricObject(color, filled);Triangle triangle = new Triangle(color, filled,side1,side2,side3);System.out.println(g.toString());System.out.println(""+triangle);System.out.println("The area is "+triangle.getArea());System.out.println("The perimeter is "+triangle.getPerimeter());input.close();}catch (IllegalTriangleException ex){System.out.println(ex.getMessage());}}
}

12.06

实现思路

Code

import java.util.Scanner;
public class exercise_12_06{public static void main(String[] args){Scanner input = new Scanner(System.in);System.out.print("Please enter a hex number: ");try {String hex = input.nextLine();System.out.println("The decimal value for hex number " + hex+"is "+hexToDec(hex.toUpperCase()));input.close();} catch (NumberFormatException ex) {System.out.println(ex);}}public static int hexToDec(String hex) throws NumberFormatException {//十六进制字符串除了在开头用0x标志之外,本身它的构成也只可能是0~1与A~Fint hexcharToDecimal=0,decimalValue=0;for(int i=0;i<hex.length();i++){char ch = hex.charAt(i);if(ch>='A' && ch<='F'){hexcharToDecimal = 10+ ch - 'A';}else if(ch>='0' && ch<='9')hexcharToDecimal = ch - '0';else//异常本身也是一种方法,故而需要()throw new NumberFormatException();decimalValue = decimalValue * 16 + hexcharToDecimal;}return decimalValue;}}

12.08

实现思路

12.11

实现思路

Code

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;
public class exercise_12_11 {public static void main(String[] args) throws FileNotFoundException {File sourceFile  = new File(args[1]);//判断文件是否存在if(!sourceFile.exists()){System.out.println("File don't exist.");}//创建一个空的字符串构建器,sb的对象为StringBuilder类Scanner input = new Scanner(sourceFile);StringBuilder sb = new StringBuilder();//在还有内容可以读的时候,不停地读入下一行while(input.hasNext()){String line = input.nextLine();//对windows而言,回车/r加换行/n才能真正换行sb.append(line.replaceAll(args[0],"")+"\r\n");}input.close();//再把内容从构建器中输出出来PrintWriter output = new PrintWriter(sourceFile);//必须使用toString()方法才可以将构建器中的字符序列输出给新的String类对象output.println(sb.toString());output.close();}
}

运行结果

从命令行传入参数
运行之前的文本:
运行之后的文本: