Memory Optimizations

Author: Rajeev Kumar Singh

java-csv-file-handling-with-apache-commons-csv/src/main/java/BasicCSVReader.java

@@ -18,9 +18,7 @@ public static void main(String[] args) throws IOException {
             Reader reader = Files.newBufferedReader(Paths.get(SAMPLE_CSV_FILE_PATH));
             CSVParser csvParser = new CSVParser(reader, CSVFormat.DEFAULT);
         ) {
-            Iterable<CSVRecord> csvRecords = csvParser.getRecords();
-
-            for (CSVRecord csvRecord : csvRecords) {
+            for (CSVRecord csvRecord : csvParser) {
                 // Accessing Values by Column Index
 
                 String name = csvRecord.get(0);

java-csv-file-handling-with-apache-commons-csv/src/main/java/CSVReaderWithHeaderAutoDetection.java

@@ -22,9 +22,7 @@ public static void main(String[] args) throws IOException {
                     .withIgnoreHeaderCase()
                     .withTrim());
         ) {
-            Iterable<CSVRecord> csvRecords = csvParser.getRecords();
-
-            for (CSVRecord csvRecord : csvRecords) {
+            for (CSVRecord csvRecord : csvParser) {
                 // Accessing values by Header names
 
                 String name = csvRecord.get("Name");

java-csv-file-handling-with-apache-commons-csv/src/main/java/CSVReaderWithManualHeader.java

@@ -23,7 +23,7 @@ public static void main(String[] args) throws IOException {
                     .withTrim());
         ) {
 
-            for (CSVRecord csvRecord : csvParser.getRecords()) {
+            for (CSVRecord csvRecord : csvParser) {
                 // Accessing values by the names assigned to each column
 
                 String name = csvRecord.get("Name");

java-csv-file-handling-with-opencsv/src/main/java/OpenCSVParseToBeanWithoutAnnotation.java

@@ -6,6 +6,7 @@
 import java.io.Reader;
 import java.nio.file.Files;
 import java.nio.file.Paths;
+import java.util.Iterator;
 import java.util.List;
 
 /**
@@ -24,15 +25,16 @@ public static void main(String[] args) throws IOException {
             String[] memberFieldsToBindTo = {"name", "email", "phoneNo", "country"};
             strategy.setColumnMapping(memberFieldsToBindTo);
 
-            CsvToBean csvToBean = new CsvToBeanBuilder(reader)
+            CsvToBean<MyUser> csvToBean = new CsvToBeanBuilder(reader)
                     .withMappingStrategy(strategy)
                     .withSkipLines(1)
                     .withIgnoreLeadingWhiteSpace(true)
                     .build();
 
-            List<MyUser> myUsers = csvToBean.parse();
+            Iterator<MyUser> myUserIterator = csvToBean.iterator();
 
-            for (MyUser myUser : myUsers) {
+            while (myUserIterator.hasNext()) {
+                MyUser myUser = myUserIterator.next();
                 System.out.println("Name : " + myUser.getName());
                 System.out.println("Email : " + myUser.getEmail());
                 System.out.println("PhoneNo : " + myUser.getPhoneNo());
@@ -41,6 +43,19 @@ public static void main(String[] args) throws IOException {
             }
         }
     }
+
+    // Reads all CSV contents into memory (Not suitable for large CSV files)
+    private static void readAllBeansAtOnce(CsvToBean csvToBean) {
+        List<MyUser> myUsers = csvToBean.parse();
+
+        for (MyUser myUser : myUsers) {
+            System.out.println("Name : " + myUser.getName());
+            System.out.println("Email : " + myUser.getEmail());
+            System.out.println("PhoneNo : " + myUser.getPhoneNo());
+            System.out.println("Country : " + myUser.getCountry());
+            System.out.println("---------------------------");
+        }
+    }
 }
 
 

java-csv-file-handling-with-opencsv/src/main/java/OpenCSVReadAndParseToBean.java

@@ -5,6 +5,7 @@
 import java.io.Reader;
 import java.nio.file.Files;
 import java.nio.file.Paths;
+import java.util.Iterator;
 import java.util.List;
 
 /**
@@ -18,14 +19,15 @@ public static void main(String[] args) throws IOException {
         try (
             Reader reader = Files.newBufferedReader(Paths.get(SAMPLE_CSV_FILE_PATH));
         ) {
-            CsvToBean csvToBean = new CsvToBeanBuilder(reader)
+            CsvToBean<CSVUser> csvToBean = new CsvToBeanBuilder(reader)
                     .withType(CSVUser.class)
                     .withIgnoreLeadingWhiteSpace(true)
                     .build();
 
-            List<CSVUser> csvUsers = csvToBean.parse();
+            Iterator<CSVUser> csvUserIterator = csvToBean.iterator();
 
-            for (CSVUser csvUser : csvUsers) {
+            while (csvUserIterator.hasNext()) {
+                CSVUser csvUser = csvUserIterator.next();
                 System.out.println("Name : " + csvUser.getName());
                 System.out.println("Email : " + csvUser.getEmail());
                 System.out.println("PhoneNo : " + csvUser.getPhoneNo());
@@ -34,6 +36,19 @@ public static void main(String[] args) throws IOException {
             }
         }
     }
+
+    // Reads all CSV contents into memory (Not suitable for large CSV files)
+    private static void readAllBeansAtOnce(CsvToBean csvToBean) {
+        List<CSVUser> csvUsers = csvToBean.parse();
+
+        for(CSVUser csvUser: csvUsers) {
+            System.out.println("Name : " + csvUser.getName());
+            System.out.println("Email : " + csvUser.getEmail());
+            System.out.println("PhoneNo : " + csvUser.getPhoneNo());
+            System.out.println("Country : " + csvUser.getCountry());
+            System.out.println("==========================");
+        }
+    }
 }
 
 

java-csv-file-handling-with-opencsv/src/main/java/OpenCSVWriter.java

@@ -52,7 +52,7 @@ private static void writeFromListOfObjects() throws IOException,
         try (
             Writer writer = Files.newBufferedWriter(Paths.get(STRING_ARRAY_SAMPLE));
         ) {
-            StatefulBeanToCsv beanToCsv = new StatefulBeanToCsvBuilder(writer)
+            StatefulBeanToCsv<MyUser> beanToCsv = new StatefulBeanToCsvBuilder(writer)
                     .withQuotechar(CSVWriter.NO_QUOTE_CHARACTER)
                     .build();