堆内存不足,java

Question

我是刚到爪哇的。我只是试图了解如何处理堆内存溢出及其原因。有人能在下面的代码中帮助我为什么它会抛出这个错误吗。我怎么能避免。

错误：

线程“main”Java.lang.OutOfMemoryError中出现异常：Java.util.arrays.copyof(arrays.Java:2361)在Java.lang.AbstractStringBuilder.ExpandCapacity（AbstractStringBuilder.Java:117)在Java.lang.AbstractStringBuilder.Append（AbstractStringBuilder.Java:406)在Java.lang.StringBuffer.Append（StringBuffer.Java:237)在com.ugam.qa.title.xlsxtocsv.xlsx

package com.ugam.qa.tittle;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.Iterator;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class XlsxToCsv {

    static void xlsx(File inputFile, File outputFile) {
        // For storing data into CSV files
        StringBuffer data = new StringBuffer();

        try {
            FileOutputStream fos = new FileOutputStream(outputFile);
            // Get the workbook object for XLSX file
            XSSFWorkbook wBook = new XSSFWorkbook(new FileInputStream(inputFile));
            // Get first sheet from the workbook
            XSSFSheet sheet = wBook.getSheetAt(0);
            Row row;
            Cell cell;
            // Iterate through each rows from first sheet
            Iterator<Row> rowIterator = sheet.iterator();

            while (rowIterator.hasNext()) {
                row = rowIterator.next();
                {
                // For each row, iterate through each columns
                Iterator<Cell> cellIterator = row.cellIterator();
                while (cellIterator.hasNext()) {

                    cell = cellIterator.next();

                    switch (cell.getCellType()) {
                        case Cell.CELL_TYPE_BOOLEAN:
                            data.append(cell.getBooleanCellValue() + ",");

                            break;
                        case Cell.CELL_TYPE_NUMERIC:
                            data.append(cell.getNumericCellValue() + ",");

                            break;
                        case Cell.CELL_TYPE_STRING:
                            data.append(cell.getStringCellValue() + ",");
                            break;

                        case Cell.CELL_TYPE_BLANK:
                            data.append("" + ",");
                            break;
                        default:
                            data.append(cell + ",");

                    }
                    data.append("\r\n");
                }}
            }

            fos.write(data.toString().getBytes());
            fos.close();

        } catch (Exception ioe) {
            ioe.printStackTrace();
        }
    }
    //testing the application 

    public static void main(String[] args) {
        //reading file from desktop
        File inputFile = new File("D:\\files\\listing\\test.xlsx");
        //writing excel data to csv 
        File outputFile = new File("D:\\files\\listing\\test1.csv");
        xlsx(inputFile, outputFile);

    }
}

Answer 1

增加堆是一种解决方案:java-xmx m

更好的解决方案是使用更少的内存，这在您的情况下很容易：为什么要在将整个输出转储到流中之前将其存储在StringBuffer中？在找到每个部分时直接将它们写入流会更节省内存。

对代码的另一个改进是使用FileWriter而不是FileOutputStream:它允许您控制输出编码，并直接接受字符串，而不需要您调用String#GetBytes()。