What is? Properties file

properties It is also a text file , Is a resource attribute file
properties Is a key value pair （key==value） To store content , Each line is a key value pair .properties Class inherits from Hashtable, You can use the key to get value value .

One 、Properties File reading

We can also regard it as the reading of ordinary files , use BufferedInputStream Read , But the key value pair is not formed after reading , So it doesn't make sense .

1.properties How the file is read

Read properties file , First, you also need to create BufferedInputSstream Buffer input stream incoming FileInputStream As a data source . Then create properties object , Call again load() Method , stay load Method into the file stream object .（ Before reading, you need to ensure that the data source you have passed in properties The file exists in the path ）
The code example is as follows ：

//Properties Format file read 
		// Create input stream 
		try (
		 BufferedInputStream input = new BufferedInputStream(new FileInputStream("c:\\text\\data.properties"))) {
    
			// establish properties File object 
			Properties pro=new Properties();
			// call load Methods , Incoming input stream 
			pro.load(input);
			
			// Print Properties object 
			System.out.println(pro);
			// Pass key key To get the value value
			System.out.println(pro.get("A1"));  //110
			System.out.println(pro.get("A3"));  //130
		} catch (IOException e1) {
    
			e1.printStackTrace();
		}

The operation result is as shown in the figure ：

Two 、properties Writing files

1.properties Brief description of the writing steps of the file ：

establish properties object , Use properties Of put Method to store key value pairs , Call again properties Of save perhaps store Method to pass in the file stream , Write key value pairs to properties file .
The code is as follows （ Example ）：

	try {
    
			Properties props=new Properties();
			props.put("A1", "110");
			props.put("A2", "120");
			props.put("A3", "130");
			props.put("A4", "140");
			
			// Create output stream , Write the above key value pair to the file *.Properties file （ namely data1.properties file )
			BufferedOutputStream out=new BufferedOutputStream(new FileOutputStream("C:\\text\\data1.properties"));
			//just do it! It's for properties Added note ,
			props.store(out, "just do it!");
			
		} catch (IOException e) {
    
			e.printStackTrace();
		}