java中 a.substrack.b
时间: 2024-03-21 10:39:55 浏览: 13
在 Java 中,字符串是不可变的对象,因此没有名为 `substrack` 的方法。如果您想从字符串 `a` 中删除字符串 `b`,可以使用 `replace` 方法将 `b` 替换为空字符串。例如,可以使用以下代码实现:
```
String a = "hello world";
String b = "world";
String result = a.replace(b, "");
System.out.println(result); // 输出 "hello "
```
在上面的代码中,首先定义了字符串 `a` 和 `b`,然后使用 `replace` 方法将字符串 `b` 替换为空字符串,并将结果保存在 `result` 变量中。最后,使用 `println` 方法将 `result` 的值输出到控制台。
相关问题
java complete Read a .csv file
To read a .csv file in Java, you can use the following steps:
1. Create a new FileReader object to read the file, passing the file name or path as a string parameter.
2. Create a new BufferedReader object, passing the FileReader object as a parameter.
3. Use the readLine method of the BufferedReader object to read each line of the file.
4. Split each line by the delimiter (usually a comma) using the split method of the String class.
5. Parse the values as needed and store them in a data structure or object.
Here is an example code snippet that demonstrates how to read a .csv file in Java:
```
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadCSVFile {
public static void main(String[] args) {
String csvFile = "data.csv";
String line = "";
String delimiter = ",";
try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {
while ((line = br.readLine()) != null) {
String[] values = line.split(delimiter);
// Do something with the values
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
```
In this example, the code reads a file named "data.csv" and splits each line by a comma delimiter. You can modify the code to handle different delimiters or to parse the values in a different way depending on your specific use case.
下面哪个集合可以存储键-值的方式?A. java.util.ArrayList B. java.util.LinkedList C. java.util.HashMap D. java.util.lterator
正确的选项是C. `java.util.HashMap`。
`java.util.ArrayList`和`java.util.LinkedList`都是列表集合,只能存储单个元素,不能存储键值对。`java.util.Iterator`是迭代器接口,不是集合类型。
而`java.util.HashMap`是一种键值对映射的集合,可以通过键来获取对应的值。例如,可以这样创建一个`HashMap`对象,存储一些键值对:
```java
HashMap<String, Integer> map = new HashMap<>();
map.put("apple", 1);
map.put("orange", 2);
map.put("banana", 3);
```
在这个例子中,我们使用字符串类型的键来存储整数类型的值。可以通过`get`方法来获取对应的值,例如:
```java
int value = map.get("apple");
System.out.println(value); // 输出1
```
因此,选项C是正确的。