java - 如何从 JavaBeanObject(泛型)写入文件

Question

我想知道如何使用 BufferedWriter 从对象(泛型)写入文件。

我尝试了下面的代码，但它不起作用。

我想打印列表中存在的所有值。我是否需要进行任何类型转换或使用迭代器并使用 get 方法或使用 for 循环。

如果我做错了什么，除了 PrintWriter 之外，还有什么方法可以将值写入文件。我尝试过使用不同的编写器，但没有任何效果。我不明白继续的方式。

取 self 的程序，该程序输出错误

    public static void file()throws Exception{
        FileWriter fw = new FileWriter("file1.txt");
        BufferedWriter bw = new BufferedWriter(fw);
    for (int i = 0; i < AllList.a.size(); i++) {

            JavaBeans b1 = AllList.a.get(i);
    bw.write(b1.getProductDescription());
    bw.flush();
    bw.close()

第二部分:

    package com.collections;

    import java.io.BufferedWriter;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.FileWriter;
    import java.io.OutputStream;
    import java.io.PrintWriter;
    import java.util.ArrayList;
    import java.util.Iterator;
    import java.util.List;

    public class AllList {
        public static List<JavaBeans> a = new ArrayList<JavaBeans>();
        public static void getAllList() {


        JavaBeans j = new JavaBeans();
        j.setProductNumber(1);
        j.setProductName("car");
        j.setProductDescription("for driving");
        j.setProductUnits(10);

        JavaBeans j1 = new JavaBeans();
        j1.setProductNumber(2);
        j1.setProductName("soap");
        j1.setProductDescription("for bathing");
        j1.setProductUnits(20);

        JavaBeans j2 = new JavaBeans();
        j2.setProductNumber(3);
        j2.setProductName("Cell");
        j2.setProductDescription("for calling");
        j2.setProductUnits(30);

        a.add(j);
        a.add(j1);
        a.add(j2);

        Iterator<JavaBeans> it = a.iterator();
        while (it.hasNext())
                {
            JavaBeans bean = it.next();
            System.out.print(bean.getProductNumber()+ " \t   "+bean.getProductDescription()+"\t"+bean.getProductName()+"\t"+bean.getProductUnits()+"\n");
        }
        }

        public static void add(JavaBeans bean )
        {
        a.add(bean);

            System.out.println("added succesfully");        
        }

        public static void update(JavaBeans bean )
        {
        for (int i = 0; i < AllList.a.size(); i++) {

            JavaBeans b = AllList.a.get(i);

            if(b.getProductNumber()==bean.getProductNumber()){
                AllList.a.set(i, bean);
            }}

        }   

        public static void delete(JavaBeans bean )
        {
        for (int i = 0; i < AllList.a.size(); i++) {

            JavaBeans b = AllList.a.get(i);

            if(b.getProductNumber()==bean.getProductNumber()){
                AllList.a.remove(i);
                System.out.println("deleted succesfully");
            }}

    }

    public static void file()throws Exception{
        FileWriter fw = new FileWriter("file1.txt");
        BufferedWriter bw = new BufferedWriter(fw);
    for (int i = 0; i < AllList.a.size(); i++) {

            JavaBeans b1 = AllList.a.get(i);
    bw.write(b1.getProductDescription());
    bw.flush();
    bw.close();
    }





                }


    }

JAVABEAN 类:

package com.collections;

public class JavaBeans {

    private int productNumber;
    private String productName;
    private String productDescription;
    private int productUnits;


    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((productDescription == null) ? 0 : productDescription.hashCode());
        result = prime * result + ((productName == null) ? 0 : productName.hashCode());
        result = prime * result + productNumber;
        result = prime * result + productUnits;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        JavaBeans other = (JavaBeans) obj;
        if (productDescription == null) {
            if (other.productDescription != null)
                return false;
        } else if (!productDescription.equals(other.productDescription))
            return false;
        if (productName == null) {
            if (other.productName != null)
                return false;
        } else if (!productName.equals(other.productName))
            return false;
        if (productNumber != other.productNumber)
            return false;
        if (productUnits != other.productUnits)
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "JavaBeans [productNumber=" + productNumber + ", productName=" + productName + ", productDescription="
                + productDescription + ", productUnits=" + productUnits + "]";
    }

    public int getProductNumber() {
        return productNumber;
    }

    public String getProductName() {
        return productName;
    }

    public String getProductDescription() {
        return productDescription;
    }

    public int getProductUnits() {
        return productUnits;
    }

    public void setProductNumber(int productNumber) {
        this.productNumber = productNumber;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public void setProductDescription(String productDescription) {
        this.productDescription = productDescription;
    }

    public void setProductUnits(int productUnits) {
        this.productUnits = productUnits;
    }

    }

Answer 1

如果您希望将可读文本打包，我建议使用 PrintWriter 进行编写 - 这会增加对代码中换行符的控制。