I am new to Java and I am trying to build a Java command-line program, which generates random dataset (as in getData()) and query into the generated dataset. But I don't know how to pass the generated data from getData() function to the main function so that I can find the oldest person in my generated data.
public class Data {
public String first;
public String last;
public int age;
public int id;
public String country;
public Data(String first, String last, int age, int id, String country) {
this.first = first;
this.last = last;
this.age = age;
this.id = id;
this.country = country;
}
public String toString() {
return "{"
" 'firstName': " first ","
" 'lastName': " last ","
" 'age': " age ","
" 'id': " id ","
" 'country': " country
" }";
}
public static ArrayList<Data> getData(int numRows) {
ArrayList<Data> generator = new ArrayList<>();
String[] names = {"James", "Matt", "Olivia", "Liam", "Charlotte", "Amelia", "Evelyn", "Taeyeon", "Sooyoung", "Tiffany", "Yoona", "Hayley"};
String[] lastName = {"Novak", "Forbis", "Corner", "Broadbet", "Kim", "Young", "Hwang", "Choi", "McDonalds", "Kentucky", "Holmes", "Shinichi"};
String[] country = {"New Zealand", "Vietnam", "Korea", "French", "Japan", "Switzerland", "Italy", "Spain", "Thailand", "Singapore", "Malaysia", "USA"};
String data = "";
Random ran = new Random();
int namesLength = numRows; // passing length to names_len
int lastNameLength = lastName.length; // passing length to lastname_len
int countryLength = country.length; // passing length to lastname_len
for (int i = 0; i < numRows; i ) { // for loop to iterate upto names.length
int x = ran.nextInt(namesLength); // generating random integer
int y = ran.nextInt(lastNameLength); // generating random integer
int z = ran.nextInt(countryLength);
int a = ran.nextInt(40);
int exampleId = ran.nextInt(1000);
// below for loop is to remove that element form names array
for (int j = x; j < (namesLength - 1); j ) {
names[j] = names[j 1]; // this moves elements to one step back
}
// below for loop is to remove that element form Lastnames array
for (int j = y; j < (lastNameLength - 1); j ) {
lastName[j] = lastName[j 1]; // this moves elements to one step back
}
for (int j = z; j < (countryLength - 1); j ) {
country[j] = country[j 1]; // this moves elements to one step back
}
namesLength = namesLength - 1; // reducing len of names_len by 1
lastNameLength = lastNameLength - 1; // reducing len of lastname_len by 1
countryLength = countryLength - 1; // reducing len of lastname_len by 1
// Output data in NDJSON format
data = "{"
" 'firstName': " names[x] ","
" 'lastName': " lastName[y] ","
" 'age': " a ","
" 'id': " exampleId ","
" 'country': " country[z]
" }";
System.out.println(data);
// How can I add data to the generator list, the generator.add(data) does not work
}
// return a list of data
return generator;
}
public static void main(String[] args) {
// Generate random data
int rows = 0;
Scanner sc = new Scanner(System.in);
System.out.print("Enter number of rows (maximum 12) you want to generate: ");
rows = sc.nextInt();
while (rows >= 13 || rows <= 0) {
System.out.println("Rows must be in range of 1 and 12");
System.out.print("Please reenter the number of rows: ");
rows = sc.nextInt();
}
System.out.println("Data is now generated");
ArrayList<Data> generatedData = getData(rows);
String[] base_options = {
"1 - Find the oldest person",
"2 - Group by country and return count",
"3 - Choose a country and group by age range",
"4 - Find the youngest person",
};
System.out.println(base_options);
// Task 2
// TODO: PASTE GENERATED DATA INTO THIS
// Find oldest
Data oldest = generatedData.stream().max((a,b) -> a.age - b.age).get();
System.out.println(String.format("The oldest person is %s %s", oldest.first, oldest.last));
CodePudding user response：
generator.add(new Data(names[x], lastName[y], a, exampleId, country[z])); works for me just fine
CodePudding user response：
You can parse your generated data in string to Data and get the max valud like this:
public static void main(String[] args) {
// Generate random data
int rows = 0;
Scanner sc = new Scanner(System.in);
System.out.print("Enter number of rows (maximum 12) you want to generate: ");
rows = sc.nextInt();
while (rows >= 13 || rows <= 0) {
System.out.println("Rows must be in range of 1 and 12");
System.out.print("Please reenter the number of rows: ");
rows = sc.nextInt();
}
System.out.println("Data is now generated");
ArrayList<String> generatedData = getData(rows);
// Find oldest
Data oldest = generatedData
.stream()
.map(it -> extractData(it))
.max(Comparator.comparingInt(a -> a.age))
.get();
System.out.println(String.format("The oldest person is %s %s", oldest.first, oldest.last));
}
private static Data extractData(String str) {
return new Data(
extractProperty(str, "firstName"),
extractProperty(str, "lastName"),
Integer.parseInt(extractProperty(str, "age")),
Integer.parseInt(extractProperty(str, "id")),
extractProperty(str, "country")
);
}
private static String extractProperty(String str, String keyName) {
String key = "'" keyName "': ";
int startIndex = str.indexOf(key) key.length();
if (startIndex < 0) {
return "";
}
StringBuilder value = new StringBuilder();
for (int i = startIndex ; i < str.length() ; i) {
char ch = str.charAt(i);
if (ch == ',') {
break;
}
value.append(ch);
}
return value.toString();
}