问题

我有一个文本文件，名为```inventory.txt```，其中包含

cats, 10, 15
dogs, 10, 15

我想要运行一段代码，在这段代码中，我可以将```cats```替换为```replacee```，将```turtles, 5, 5```替换为```replacer```，得到

turtles, 5, 5
dogs, 10, 15

然而，当我这样做时，第一个逗号后面的所有内容仍然与我的```replacer```一起。我可以将```cats```仅替换为```turtles```，而不包括```5, 5```，这将给我

turtles, 10, 15
dogs, 10, 15

但是，当我尝试在第一个逗号之后添加```5, 5```时，它仍然保留在输出中，如下所示。

**代码**
```java
public void modifyItems() throws IOException {
		
	File file = new File("src/inventory.txt");
	String line = "";
	String oldLine = "";
	String replacee;
	String replacer;
		
	BufferedReader reader = new BufferedReader(new FileReader(file));

	while ((line = reader.readLine()) != null) {
		oldLine += line + System.lineSeparator();
			
	}
	System.out.println(oldLine);
	reader.close();
		
	System.out.println("输入要编辑的项目");
	replacee = scan.next();
	scan.nextLine();
	System.out.println("输入更新的信息");
	replacer = scan.nextLine();
	String newLine = oldLine.replaceAll(replacee, replacer);
		
	BufferedWriter writer = new BufferedWriter(new FileWriter(file));
	writer.write(newLine);
	writer.flush();
	writer.close();
}

输出

cats, 10, 15
dogs, 10, 15

输入要编辑的项目
cats
输入更新的信息
turtles, 5, 5

文本文件输出

turtles, 5, 5, 10, 15
dogs, 10, 15

<details>
<summary>英文:</summary>

I have a textfile, ```inventory.txt```, with 

cats, 10, 15
dogs, 10, 15

I want to run a code where I can input ```cats``` as ```replacee``` and ```turtles, 5, 5``` as the ```replacer```, giving me, 

turtles, 5, 5
dogs, 10, 15

however, when I do this, everything after the first comma remains in addition to my ```replacer```. I can replace ```cats``` with JUST ```turtles``` with no ```5, 5```, giving me 

turtles, 10, 15
dogs, 10, 15

but when I try adding the ```5, 5``` after the first comma remains, output below.


**Code**

public void modifyItems() throws IOException {

	File file = new File("src/inventory.txt");
	String line = "";
	String oldLine = "";
	String replacee;
	String replacer;
	
	BufferedReader reader = new BufferedReader(new FileReader(file));

	while ((line = reader.readLine()) != null) {
		oldLine += line + System.lineSeparator();
		
	}
	System.out.println(oldLine);
	reader.close();
	
	System.out.println("enter the item you want to edit");
	replacee = scan.next();
	scan.nextLine();
	System.out.println("enter the updated information");
	replacer = scan.nextLine();
	String newLine = oldLine.replaceAll(replacee, replacer);
	
	BufferedWriter writer = new BufferedWriter(new FileWriter(file));
	writer.write(newLine);
	writer.flush();
	writer.close();
}

**Output**

cats, 10, 15
dogs, 10, 15

enter the item you want to edit
cats
enter the updated information
turtles, 5, 5

**Textfile output**

turtles, 5, 5, 10, 15
dogs, 10, 15

</details>


# 答案1
**得分**: 0

```java
// 字符串的 `replaceAll` 方法执行的是你在代码中看到的操作。
// 它会将你输入的文本替换为你输入的库存字符串。

// 你需要使用的方法是字符串的 `startsWith` 方法。

// 你需要保留一个已读行的数组，这样你就可以找到要替换的正确行。

public void modifyItems() throws IOException {

    File file = new File("src/inventory.txt");

    // 将100替换为足够大的数字，以容纳整个文件。
    String[] oldLine = new String[100];

    BufferedReader reader = new BufferedReader(
            new FileReader(file));
    int count = 0;
    String line = "";
    while ((line = reader.readLine()) != null) {
        oldLine[count] = line + System.lineSeparator();
        System.out.println(line);
        count++;
    }
    reader.close();

    System.out.println("输入要编辑的项目");
    String replacee = scan.nextLine();
    System.out.println("输入更新后的信息");
    String replacer = scan.nextLine();

    BufferedWriter writer = new BufferedWriter(
            new FileWriter(file));
    for (int i = 0; i < count; i++) {
        if (oldLine[i].startsWith(replacee)) {
            writer.write(replacer);
        } else {
            writer.write(oldLine[i]);
        }
    }
    writer.flush();
    writer.close();
}

public void modifyItems() throws IOException {

	File file = new File("src/inventory.txt");

	// Replace 100 with a large enough number to hold
	// the whole file.
	String[] oldLine = new String[100];

	BufferedReader reader = new BufferedReader(
			new FileReader(file));
	int count = 0;
	String line = "";
	while ((line = reader.readLine()) != null) {
		oldLine[count] = line + System.lineSeparator();
		System.out.println(line);
		count++;
	}
	reader.close();
	
	System.out.println("enter the item you want to edit");
	String replacee = scan.nextLine();
	System.out.println("enter the updated information");
	String replacer = scan.nextLine();

	BufferedWriter writer = new BufferedWriter(
			new FileWriter(file));
	for (int i = 0; i < count; i++) {
		if (oldLine[i].startsWith(replacee)) {
			writer.write(replacer);
		} else {
			writer.write(oldLine[i]);
		}
	}
	writer.flush();
	writer.close();
}