嘿大家所以我有一个非常大的数组，其中列出了名称和受欢迎程度等级，通常数字越低，该名称越受欢迎。我需要一种方法来搜索数组，找出特定十年中20个最低数字。那么让我告诉你我的列表和代码是什么。
这是我的代码：
名称
public class Name{
private String givenName;
private int[] ranks = new int[11];
public Name(String name, int[] popularityRanks){
givenName = name;
for (int i = 0; i < 11; i++){
ranks[i] = popularityRanks[i];
}
}
public String getName(){
return givenName;
}
public int getPop(int decade){
if (decade >= 1 && decade <= 11){
return ranks[decade];
}
else{
return -1;
}
}
public String getHistoLine(int decade){
String histoLine = ranks[decade] + ": ";
return histoLine;
}
public String getHistogram(){
String histogram = "";
for (int i = 0; i < 11; i++){
histogram += ranks[i] + ": " + this.getHistoLine(i)
+ "\n";
}
return histogram;
}
}
然后是NameApp：
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
public class NameApp{
private static boolean validInput;
private static boolean stillWorking = true;
private static boolean validDecade;
static Scanner keyboard = new Scanner(System.in);
public static void main(String[] args) throws FileNotFoundException{
String[] nameArray = readNamesFile();
Name[] list = new Name[nameArray.length];
loadNames(list, nameArray);
char choice;
do {
do {
displayMenu();
choice = getUserInput();
} while (!validInput);
switch (choice){
case 'A':
displayHistogram(list);
break;
case 'B':
compareTwoNames(list);
break;
case 'C':
displayTopTenNames(list);
break;
case 'D':
writeAnomaliesToFile(list);
stillWorking = false;
break;
default:
break;
}
} while (stillWorking);
}
private static String[] readNamesFile() throws FileNotFoundException{
String[] nameArray = new String[4429];
Scanner inputStream = null;
String fileName = "names.txt";
inputStream = new Scanner (new File(fileName));
int i = 0;
while (inputStream.hasNextLine()){
nameArray[i] = inputStream.nextLine();
i++;
}
inputStream.close();
return nameArray;
}
private static void loadNames(Name[] list, String[] nameArray){
int length;
int spacePos;
int[] popRanks = new int[11];
String name;
String linePop;
for (int i = 0; i < nameArray.length; i++){
length = nameArray[i].length();
spacePos = nameArray[i].indexOf(" ");
name = nameArray[i].substring(0,spacePos);
linePop = nameArray[i].substring(spacePos + 1, length);
for (int j = 0; j < 11; j++){
popRanks[j] = Integer.parseInt(linePop.split(" ")[j]);
}
list[i] = new Name(name, popRanks);
}
}
private static void displayMenu(){
System.out.println("Enter the character corresponding to your selection:");
System.out.println("\ta - Print histogram for a name");
System.out.println("\tb - Compare two names in a decade");
System.out.println("\tc - Print top ten names for a decade");
System.out.println("\td - Quit (display file anomalies)");
}
private static char getUserInput(){
String selection = keyboard.nextLine();
System.out.println(" Your selection: " + selection);
checkUserInput(selection);
char choice = stringToChar(selection);
return choice;
}
private static boolean checkUserInput(String selection){
if (!selection.equalsIgnoreCase("a") && !selection.equalsIgnoreCase("b") && !selection.equalsIgnoreCase("c") && !selection.equalsIgnoreCase("d")){
System.out.println("Invalid input. Try again...");
return validInput = false;
}
else {
return validInput = true;
}
}
private static char stringToChar(String selection){
char choice = selection.charAt(0);
choice = Character.toUpperCase(choice);
return choice;
}
private static void displayHistogram(Name[] list){
String nameInput;
String histogram;
int nameLocation;
nameInput = nameEntry();
nameLocation = checkListArray(nameInput, list);
histogram = list[nameLocation].getHistogram();
System.out.println("Histogram for name, " + list[nameLocation].getName() + ":");
System.out.println(histogram);
}
private static void compareTwoNames(Name[] list){
String nameOne;
String nameTwo;
String oneHistoLine;
String twoHistoLine;
int oneLocation;
int twoLocation;
int decade;
nameOne = nameEntry();
oneLocation = checkListArray(nameOne, list);
nameTwo = nameEntry();
twoLocation = checkListArray(nameTwo, list);
decadeMenu();
decade = decadeSelection();
oneHistoLine = list[oneLocation].getHistoLine(decade);
twoHistoLine = list[twoLocation].getHistoLine(decade);
System.out.println("Data for " + list[oneLocation].getName());
System.out.println(" " + oneHistoLine);
System.out.println("Data for " + list[twoLocation].getName());
System.out.println(" " + twoHistoLine);
}
private static void displayTopTenNames(Name[] list){
int decade;
int temp = 1000;
int tempTwo;
String[] topTen = new String[20];
decadeMenu();
decade = decadeSelection();
for (int i = 0; i < 20; i++){
for (int j = 0; j < list.length; j++){
if (list[j].getPop(decade) > 0 && list[j].getPop(decade) < temp){
temp = list[j].getPop(decade);
tempTwo =
}
}
}
}
private static void writeAnomaliesToFile(Name[] list){
}
private static String nameEntry(){
String nameInput = "";
System.out.println("Enter a name: ");
nameInput = keyboard.nextLine();
return nameInput;
}
private static int checkListArray(String nameInput, Name[] list){
int nameLocation = -1;
int listLength = list.length;
for (int i = 0; i < listLength; i++){
if (nameInput.equalsIgnoreCase(list[i].getName())){
return nameLocation = i;
}
}
if (nameLocation == -1){
System.out.println("The name, " + nameInput + ", was not found!");
return nameLocation;
}
return nameLocation;
}
private static void decadeMenu(){
System.out.println("Enter number correpsonding to your decade:");
System.out.println(" 1 - 1900-1909");
System.out.println(" 2 - 1910-1919");
System.out.println(" 3 - 1920-1929");
System.out.println(" 4 - 1930-1939");
System.out.println(" 5 - 1940-1949");
System.out.println(" 6 - 1950-1959");
System.out.println(" 7 - 1960-1969");
System.out.println(" 8 - 1970-1979");
System.out.println(" 9 - 1980-1989");
System.out.println(" 10 - 1990-1999");
System.out.println(" 11 - 2000-2005");
}
private static int decadeSelection(){
String decadeChoice;
int decade;
do {
System.out.println("Enter a decade: ");
decadeChoice = keyboard.nextLine();
decade = checkDecade(decadeChoice);
} while (!validDecade);
return decade;
}
private static int checkDecade(String decadeChoice){
int decade = 0;
try {
decade = Integer.parseInt(decadeChoice);
}
catch (Exception e){
System.out.println("That is not an integer. Please try again.");
return decade;
}
if (decade < 1 || decade > 11){
System.out.println("Enter an integer between 1 and 11");
validDecade = false;
return decade;
}
else {
validDecade = true;
return decade;
}
}
}
所以我需要帮助的是displayTopTenNames方法。我有点搞砸了它，但是我提出的每个循环总是会产生我不想要的重复...无论如何我的输出应该是这样的：
1910 - 1919年间十个最受欢迎的名字（男性和女性）是：
约翰（1）玛丽（1）所以，非常感谢您的帮助，并提前致谢。
答案 0 :(得分：0)
查看Arrays.sort（）方法：
http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html
答案 1 :(得分：0)
可能有更有效的方法来做到这一点，但这显示了理论。您维护一个包含20个项目的小清单。您扫描大型列表以查看它是否是您的短名单的候选者。如果列表小于20，则会添加任何内容。如果已达到20，则检查列表中的任何内容是否大于您要添加的项目。如果是，则该项目被驱逐并用较小的值替换。
public class Low20 {
private List<Integer> list = new ArrayList<Integer>();
public static final void main(String[] args) {
new Low20();
}
public Low20() {
Random random = new Random();
for (int x=0;x<100000;x++) {
add(random.nextInt(100000));
}
System.out.println(list);
}
public void add(int value) {
if (list.size() < 20) {
list.add(value);
} else {
for (int x=0;x<list.size();x++) {
if (list.get(x) > value) {
list.remove(x);
list.add(value);
return;
}
}
}
}
}
结果。 （随机数，但最低20）。然后，您可以对这些进行排序，或将排序合并到逐出算法中。
[6,0,5,17,18,11,10,27,22,27,28,16,34,33,0,8,28,0,15,14]
此方法优于在列表中使用毯式排序，这是因为您的列表不必适合内存，可以从文件或数据库扫描中应用。