我有一个csv文件，其中包含50个州，四个地区（东北，西部等）和波多黎各的人口记录，因此有超过50行数据。我需要找到人口增加的状态数，所以我不想检查所有行，只有50个状态用于50个状态，第6个元素到第56个元素。我相信ArrayList的子列表是要走的路，但是我该怎么编码呢？这是我正在处理的代码部分：
// Number of states with estimated population increase in 2011
int x = 0;
// al = arrayList.subList(6,56);
for (int i = 0; i < popList.size(); i++) {
PopulationRecord pr1 = popList.get(i);
if (pr1.getPopch2011() > 0) {
x++;
}
}
System.out.println("Number of states with estimated population increase in 2011 is " + n);
以下是我在驱动程序类中的其余代码：
package miniproj2;
import domain.PersistentObject;
import domain.PopulationRecord;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import utilities.MiniProj2Utilities;
import domain.CensusComparator;
/**
*
* @author
*/
public class MiniProj2Driver {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// Make sure that you develop your main() method with reduced code as shown below.
// Not the use of private static methods in the driver called from main() method.
// Read the CSV file records into a list of PopulationRecord objects...
List<PopulationRecord> popList = MiniProj2Utilities.getDataRecords();
// Display the list contents and size...
MiniProj2Utilities.displayRecordsFromList(popList);
// Create and populate the PersistentObject...
PersistentObject po = MiniProj2Utilities.getPersistentObject(popList);
try {
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("./data/population-record.ser"));
oos.writeObject(po);
} catch (IOException ex) {
}
long serializedTime = System.currentTimeMillis();
System.out.println(po);
try {
Thread.sleep(5000);
} catch (InterruptedException ex) {
System.out.println("Sleep Error");
}
try {
ObjectInputStream oos = new ObjectInputStream(new FileInputStream("./data/population-record.ser"));
PersistentObject po1 = (PersistentObject) oos.readObject();
} catch (IOException ex) {
} catch (ClassNotFoundException ex) {
}
System.out.println("Time waited is: " + (serializedTime - System.currentTimeMillis()) / 1000 + " secs.");
// Maximum births for 2010 and 2011
PopulationRecord max = popList.get(0);
for (int i = 0; i < popList.size(); i++) {
if (CensusComparator.compareBirths(max, popList.get(i)) == 1) {
max = popList.get(i);
}
}
System.out.println("Maximum births for 2010 is " + max.getBirths2010());
System.out.println("Maximum births for 2011 is " + max.getBirths2011());
// Minimum births for 2010 and 2011
PopulationRecord min = popList.get(0);
for (int i = 0; i < popList.size(); i++) {
if (CensusComparator.compareBirths(min, popList.get(i)) == -1) {
min = popList.get(i);
}
}
System.out.println("Minimum births for 2010 is " + min.getBirths2010());
System.out.println("Minimum births for 2011 is " + min.getBirths2011());
// Population % increase per region for 2010
for (int i = 0; i < popList.size(); i++) {
PopulationRecord pr1 = popList.get(i);
float inc = 0;
if (pr1.getName().equals("Northeast Region")) {
inc = ((float) pr1.getPopch2010() / (float) pr1.getPopest2010()) * 100;
System.out.println("Estimated population increase for 2010 in Northesast Region is " + inc);
} else if (pr1.getName().equals("Midwest Region")) {
inc = ((float) pr1.getPopch2010() / (float) pr1.getPopest2010()) * 100;
System.out.println("Estimated population increase for 2010 in Midwest Region is " + inc);
} else if (pr1.getName().equals("South Region")) {
inc = ((float) pr1.getPopch2010() / (float) pr1.getPopest2010()) * 100;
System.out.println("Estimated population increase for 2010 in South Region is " + inc);
} else if (pr1.getName().equals("West Region")) {
inc = ((float) pr1.getPopch2010() / (float) pr1.getPopest2010()) * 100;
System.out.println("Estimated population increase for 2010 in West Region is " + inc);
}
}
// Population % increase per region for 2011
for (int i = 0; i < popList.size(); i++) {
PopulationRecord pr1 = popList.get(i);
float inc = 0;
if (pr1.getName().equals("Northeast Region")) {
inc = ((float) pr1.getPopch2011() / (float) pr1.getPopest2011()) * 100;
System.out.println("Estimated population increase for 2011 in Northesast Region is " + inc);
} else if (pr1.getName().equals("Midwest Region")) {
inc = ((float) pr1.getPopch2011() / (float) pr1.getPopest2011()) * 100;
System.out.println("Estimated population increase for 2011 in Midwest Region is " + inc);
} else if (pr1.getName().equals("South Region")) {
inc = ((float) pr1.getPopch2011() / (float) pr1.getPopest2011()) * 100;
System.out.println("Estimated population increase for 2011 in South Region is " + inc);
} else if (pr1.getName().equals("West Region")) {
inc = ((float) pr1.getPopch2011() / (float) pr1.getPopest2011()) * 100;
System.out.println("Estimated population increase for 2011 in West Region is " + inc);
}
}
// Number of states with estimated population increase in 2010
int n = 0;
for (int i = 0; i < popList.size(); i++) {
PopulationRecord pr1 = popList.get(i);
if (pr1.getPopch2010() > 0) {
n++;
}
}
System.out.println("Number of states with estimated population increase in 2010 is " + n);
// Number of states with estimated population increase in 2011
int x = 0;
al = arrayList.subList(6,56);
for (int i = 0; i < popList.size(); i++) {
PopulationRecord pr1 = popList.get(i);
if (pr1.getPopch2011() > 0) {
x++;
}
}
System.out.println("Number of states with estimated population increase in 2011 is " + n);
// Number of states with estimated population decrease in 2010
int y = 0;
for (int i = 0; i < popList.size(); i++) {
PopulationRecord pr1 = popList.get(i);
if (pr1.getPopch2010() < 0) {
y++;
}
}
System.out.println("Number of states with estimated population decrease in 2010 is " + y);
// Number of states with estimated population decrease in 2011
int z = 0;
for (int i = 0; i < popList.size(); i++) {
PopulationRecord pr1 = popList.get(i);
if (pr1.getPopch2011() > 0) {
z++;
}
}
System.out.println("Number of states with estimated population decrease in 2011 is " + z);
// State with highest estimated population decrease for 2010
PopulationRecord max3 = popList.get(6);
for (int i = 6; i < popList.size(); i++) {
if (CensusComparator.comparePop2010(max3, popList.get(i)) == 1) {
max3 = popList.get(i);
}
}
System.out.println("State with highest estimated population for 2010 is " + max3.getName());
// State with highest estimated population increase for 2011
PopulationRecord max4 = popList.get(6);
for (int i = 6; i < popList.size(); i++) {
if (CensusComparator.comparePop2011(max4, popList.get(i)) == 1) {
max4 = popList.get(i);
}
}
System.out.println("State with highest estimated population for 2011 is " + max4.getName());
// State with lowest estimated population increase for 2010
PopulationRecord min2 = popList.get(6);
for (int i = 6; i < popList.size(); i++) {
if (CensusComparator.comparePopul2010(min2, popList.get(i)) == 1) {
min2 = popList.get(i);
}
}
System.out.println("State with lowest estimated population for 2010 is " + min2.getName());
// State with lowest estimated population increase for 2011
PopulationRecord min3 = popList.get(6);
for (int i = 6; i < popList.size(); i++) {
if (CensusComparator.comparePopul2011(min3, popList.get(i)) == 1) {
min3 = popList.get(i);
}
}
System.out.println("State with lowest estimated population for 2011 is " + min3.getName());
}
// Read the CSV file records into a list of PopulationRecord objects...
private static List<PopulationRecord> getDataRecords() {
BufferedReader br = null;
String line = null;
List<PopulationRecord> list = new ArrayList<PopulationRecord>();
try {
br = new BufferedReader(new FileReader("data/NST_EST2011_ALLDATA.csv"));
br.readLine(); // Remove header line from file...
while ((line = br.readLine()) != null) {
String[] tokens = line.split(",");
//System.out.println(line);
PopulationRecord pr = new PopulationRecord(
tokens[0], tokens[1], tokens[2], tokens[3], tokens[4],
Integer.parseInt(tokens[5]), Integer.parseInt(tokens[6]),
Long.parseLong(tokens[7]), Long.parseLong(tokens[8]),
Long.parseLong(tokens[9]), Long.parseLong(tokens[10]),
Long.parseLong(tokens[11]), Long.parseLong(tokens[12]),
Long.parseLong(tokens[13]), Long.parseLong(tokens[14]),
Long.parseLong(tokens[15]), Long.parseLong(tokens[16]),
Long.parseLong(tokens[17]), Long.parseLong(tokens[18]),
Long.parseLong(tokens[19]), Long.parseLong(tokens[20]),
Long.parseLong(tokens[21]), Long.parseLong(tokens[22]),
Long.parseLong(tokens[23]), Float.parseFloat(tokens[24]),
Float.parseFloat(tokens[25]), Float.parseFloat(tokens[26]),
Float.parseFloat(tokens[27]), Float.parseFloat(tokens[28]),
Float.parseFloat(tokens[29]));
list.add(pr);
}
} catch (FileNotFoundException ex) {
Logger.getLogger(MiniProj2Driver.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(MiniProj2Driver.class.getName()).log(Level.SEVERE, null, ex);
}
return list;
}
// Display the list contents and size...
private static void displayRecordsFromList(List<PopulationRecord> list) {
for (PopulationRecord record : list) {
System.out.println(record);
}
System.out.println("Population records processed: " + list.size() + list.get(9));
}
private static PersistentObject getPersistentObject(List<PopulationRecord> list) {
PersistentObject po = new PersistentObject();
po.setSerializedTime(new Date());
po.setPopulationList(list);
return po;
}
}
答案 0 :(得分：4)
您也可以尝试：
for(PopulationRecord pr1 : popList.subList(5, 56)) {
if (pr1.getPopch2011() > 0) {
x++;
}
}
答案 1 :(得分：1)
您可以简单地将i初始化为5，并在i == 56时停止。
答案 2 :(得分：0)
正如awolfe91所述，只是
// Number of states with estimated population increase in 2011
int x = 0;
// al = arrayList.subList(6,56);
for (int i = 5; i < popList.size(); i++) {
if(i == 56) break;
PopulationRecord pr1 = popList.get(i);
if (pr1.getPopch2011() > 0) {
x++;
}
}
System.out.println("Number of states with estimated population increase in 2011 is " + n);
根据需要对数组列表进行切片。您可以编写像
这样的实用程序public static <T> List<T> slice(List<T> list, int index, int count) {
List<T> result = new ArrayList<T>();
if (index >= 0 && index < list.size()) {
int end = index + count < list.size() ? index + count : list.size();
for (int i = index; i < end; i++) {
result.add(list.get(i));
}
}
return result;
}
检查示例代码here。