代写program、代写Python，Java编程

日期：2023-05-24 10:08

File Input lab

The dataset in the info.txt file contains information from the World Happiness Report in 2022 collected by

Gallup.

Below are descriptions of each value. Each line represents data for one country. Each value in the line is

separated by a tab. For each line, the values are in the following order:

1. Country Name

2. Regional Indicators: CentralEastEurope, Asia, LatinAmerica, MiddleEastNorthAfrica, NorthAmericaANZ,

Africa, WesternEurope

3. GDP per capita is in terms of Purchasing Power Parity (PPP) adjusted to a constant 2017 international

dollars, taken from the World Development Indicators (WDI) by the World Bank (version 17, metadata last

updated on January 22, 2023). See Statistical Appendix 1 for more details. GDP data for 2022 are not yet

available, so we extend the GDP time series from 2021 to 2022 using country-specific forecasts of real GDP

growth from the OECD Economic Outlook No. 112 (November 2022) or, if missing, from the World Bank’s

Global Economic Prospects (last updated: January 10, 2023), after adjustment for population growth.

4. Freedom to make life choices (0-1) is the national average of binary responses to the GWP question "Are

you satisfied or dissatisfied with your freedom to choose what you do with your life?"

5. Happiness score (0-10) national average response to the question "Please imagine a ladder, with steps

numbered from 0 at the bottom to 10 at the top. The top of the ladder represents the best possible life for

you and the bottom of the ladder represents the worst possible life for you. On which step of the ladder

would you say you personally feel you stand at this time?"

Exceptional values

Data for some countries have not been included in the dataset. These values are "NA" instead of a numeric

value. The count of the number of countries in a region should not be affected by “NA”. The total number of

countries should be the same in the calculator of average GDP, average happiness score, and average

freedom score.

Converting a digit String into a double

You may need to use the Double.parseDouble method from the Wrapper class to convert a String into

a Double object. Call the method with a String argument and it will return a Double. The String

argument may only contain digit, ‘+’, or ‘-’ characters.

Using constants

When your data is divided up by categories, you can make the logic easier for your reader to understand by

introducing constants. Constants are variables that cannot change value during a program. In Java, a variable

is declared as a constant with the keyword final. By convention, we give constants a name all in capital

letters. For example, if your program contains the line:

final int AFRICA=0;

it can use AFRICA as the index number for all African data (in that row or column).

switch statements

Instead of using if-else if- else blocks, you can use a switch statement. The code is often easier to

write and read. See the syntax and example below. A switch statement can contain as many cases

needed.

switch(switch expression that holds a primitive value or String){

case value1(constant variable OR value with type that matches switch expression):

code;

//as many statements as need

break; (if no return statement)

case value2(constant variable OR value with type that matches switch expression):

code;

//as many statements as you need

break; (if no return statement)

…

default: (optional case that runs if no other case runs)

}

printf formatting

The printf method (from the same class as print and println) can be used to print formatted text in

many ways. To format text so that text is padded with extra spaces, you can set the width of the field. The

width represents the total number of characters printed. If the String contains fewer characters than the size of

the field’s width, spaces will be added before or after the String.

For example:

System.out.printf("%10s", "Test");

will print six spaces and then Test: Test

4

To print a String and then pad with spaces after, you include - before the size of the width.

For example:

System.out.printf("%-10s", "Test");

System.out.print("done");

will print Test and then six spaces:Test done

To print many different strings with different paddings, you can use many %width

For example:

System.out.printf("%-5s%-5s%5s%5s","a","b","c","d");

will print a with 4 padded spaces after, then b with 4 padded spaces after, then 4 padded spaces with c after,

then 4 padded spaces with d after:a b c d

To print a floating point value with a certain number of decimal places with a given width, you can also use the

printf method. The method will round to eliminate decimal places.

For example to print with 2 decimal places after:

System.out.printf("%10.2f", 1234.5678);

will print three spaces and then 1234.57: 1234.57

To print a floating point value with a certain number of decimal places with a given width and padding after use

the - character as before.

For example:

System.out.printf("%-10.3f", 1234.5678);

System.out.print("done");

will print 1234.568 and then two spaces:1234.568 done

Closing a Scanner instance

At the end of a method, you can close the stream on a Scanner object with the close instance method.

Often, this is optional; not closing the Scanner will not affect your program.

Assignment

To read the data in the file, you will need to set the line delimiter to a tab. In order to do so, call the

useDelimiter method with the appropriate Scanner instance. The argument will be the String that

represents a tab. Any method that uses a Scanner to read file input or calls a method that does so must

contain the code throws Exception in the header!

The class contains several variable declarations. dataTable is a 2D array of doubles that will hold the

average values for the data in each region. The 2D array should have 7 rows and 3 columns. Each row

represents one region. The first column should hold the average GDP, the second column should hold the

average Freedom Score, and the last column should hold the average Happiness Score. Class constants

have also been declared for each region. Consider using them in your program! Finally, a variable will store

the happiness score for the United States.

You must implement 5 methods. You may choose to write any private helper methods you want in addition to

these:

1) constructor: this method should initialize all instance variables and by the time the method is finished

executing, dataTable should contain all necessary averages

2) printData(): this method will print the formatted values stored in dataTable for the three 3 data

types for each region as shown below. The GDP should be formatted to 2 decimal places and start

with the ‘$’ symbole. The Freedom Score and Happiness Score should be formatted to 3 decimal

places. This method should not return a value.

The header should be the text labels each printed in a field of 20 characters (width of 20, with padding after).

You will need to figure out the code for this!

The label at the beginning of each row should be the text in a field of 20 characters (width of 20, with padding

after).

System.out.printf("%-20s",text label goes here);

The GDP value should be a floating point number with 2 decimal places in a field of 20 characters (width of 20,

with padding after). You can use:

System.out.printf("%-20.2f", floating value goes here)

The freedom score and happiness scores should be a floating point number with 3 decimal places in a field of

20 characters (width of 20, with padding after).

System.out.printf("%-20.3f", floating value goes here)

The first few lines that should be printed have been filled in for you. The total width of the field for the GDP

column will have a width of 21 characters (a width of 20 characters for the digits and one additional for the ‘$’

symbol).

World Region GDP Freedom Score Happiness Score

Africa $4552.58 0.707 4.549

Asia $13510.99 0.809 5.185

East Europe

Latin Amer

Middle East

N. Amer/ANZ

West Europe

3) poorButHappy(): returns an ArrayList of String country names (in alphabetic order) for which

the GDP is below the region’s average AND the happiness score is above the region’s average. The

country names are the names in the info.txt file.

4) freedomDifference(): returns a String that states the difference between the regions with the

highest and lowest average freedom scores (the scores in the data table, not the printed values). The

regional names should match those in the info.txt file. For example, if the maximum freedom score was

0.982 for WesternEurope and the lowest score was 0.651 for CentralEastEurope the returned String

should be "WesternEurope had the maximum freedom score and CentralEastEurope had the minimum

freedom score. The difference was 0.331." If two regions have the same minimum or maximum score,

store the first minimum score or first maximum score.

5) happierThanUs(): returns an ArrayList of String country names (in alphabetic order) for

which the Happiness Score is above the happiness score for the United States. The country names

are the names in the info.txt file.