java实现简单的增删改查
时间: 2023-05-24 13:03:33 浏览: 52
A:
增加数据:
```java
public static void addData(String newData) {
try {
FileWriter writer = new FileWriter("data.txt", true);
writer.write(newData + "\n");
writer.close();
System.out.println("数据已添加!");
} catch (IOException e) {
e.printStackTrace();
}
}
```
删除数据:
```java
public static void deleteData(String data) {
try {
File inputFile = new File("data.txt");
File tempFile = new File("temp.txt");
BufferedReader reader = new BufferedReader(new FileReader(inputFile));
BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));
String lineToRemove = data;
String currentLine;
while ((currentLine = reader.readLine()) != null) {
String trimmedLine = currentLine.trim();
if (trimmedLine.equals(lineToRemove)) {
continue;
} else {
writer.write(currentLine + System.getProperty("line.separator"));
}
}
writer.close();
reader.close();
boolean successful = tempFile.renameTo(inputFile);
if (successful) {
System.out.println("数据已删除!");
}
} catch (IOException e) {
e.printStackTrace();
}
}
```
更改数据:
```java
public static void updateData(String oldData, String newData) {
try {
File inputFile = new File("data.txt");
File tempFile = new File("temp.txt");
BufferedReader reader = new BufferedReader(new FileReader(inputFile));
BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));
String lineToReplace = oldData;
String newLine = newData;
String currentLine;
while ((currentLine = reader.readLine()) != null) {
String trimmedLine = currentLine.trim();
if (trimmedLine.equals(lineToReplace)) {
writer.write(newLine + System.getProperty("line.separator"));
} else {
writer.write(currentLine + System.getProperty("line.separator"));
}
}
writer.close();
reader.close();
boolean successful = tempFile.renameTo(inputFile);
if (successful) {
System.out.println("数据已更改!");
}
} catch (IOException e) {
e.printStackTrace();
}
}
```
查询数据:
```java
public static void searchData(String data) {
try {
BufferedReader reader = new BufferedReader(new FileReader("data.txt"));
String currentLine;
while ((currentLine = reader.readLine()) != null) {
String trimmedLine = currentLine.trim();
if (trimmedLine.equals(data)) {
System.out.println("查询到的数据为:" + currentLine);
}
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
```
以上代码实现了一个简单的增删改查操作,使用文件存储数据。如果需要更高效的数据库操作,可以考虑使用Java的JDBC或其他框架。