Properties [key details]

1, Introduction & overview

Why use Properties: to save the configuration information of the program more professionally.   Configuration information: information required for program running Program A: User name = zhangsan Password =xxxx IP=192.168.36.11 Authority = administrator Code table =utf-8   The Properties class represents a persistent property set, which can store key value pairs (hashmaps) like the Map set   Persistent: save data from memory to hard disk All Key value s are strings

 

 

2, Entry case: adding key value pairs

Properties persist data on the hard disk.

It's equivalent to HashMap, unordered, with key value. Both key and value are strings

/*
* Getting started: adding key value pairs to Properties
* HashMap
* */
@Test
public void run1(){
    //1. The key value of the created object is String
    Properties p = new Properties();
    //2. Add key value pair
    //2.1. Add key value pair: setProperty(key,value) is equivalent to map put (key, value), with the same effect
    p.setProperty("k1","v1");
    p.setProperty("k2","v2");
    p.setProperty("k2","v3");
    //2.2. Get key value pair: getProperty(key) is equivalent to map get (key), with the same effect
    String k2 = p.getProperty("k2");
    System.out.println(k2);
    System.out.println(p);
    //3, traversal
    //3.1. Turn Properties into Set set Set. All key s are saved in the Set set
    Set<String> set = p.stringPropertyNames();
    //3.2 traverse Set set
    for (String key : set) {
        System.out.println(key+"----------"+p.getProperty(key));
    }
}

 

 

 

3, Advanced case 1: write data operation byte stream

To write out the configuration file

/*
*   Save the key value pair to Properties and write it out as a configuration file
*   Byte: Universal
*   character
*  */
@Test
public void run1() throws Exception {
    //1. Create the Properties object and save the data
    Properties p = new Properties();
    p.setProperty("name","Eldest brother");
    p.setProperty("sex","Pure men");
    p.setProperty("age","18");
    //2. Create output stream object extension must be:. properties
    FileOutputStream fos = new FileOutputStream("pd.properties");
    //3. Write out file: store store
    p.store(fos,"This is the big brother's message");
    //4, Guan Liu
    fos.close();
}

 

 

 

4, Advanced case 2: read data operation byte stream

To read the configuration file

/*
* Read data from Properties file
* */
@Test
public void run2() throws Exception {
    //1. Create Properties object (ready to read data)
    Properties p = new Properties();
    //2. To create an input stream, the read file extension must be:. properties
    FileInputStream fis = new FileInputStream("pd.properties");
    //3. Read load / read
    p.load(fis);
    System.out.println(p);
    //4, Guan Liu
    fis.close();
}

 

 

5, Advanced case 3: byte stream character stream comparison

Write in byte stream:

/*
* Read with character stream
* */
@Test
public void run3() throws Exception {
    //1. Create Properties object (ready to read data)
    Properties p = new Properties();
    //2. To create an input stream, the read file extension must be:. properties
    FileReader fr = new FileReader("Byte stream.properties");
    //3. Read load / read
    p.load(fr);
    System.out.println(p);
    //4, Guan Liu
    fr.close();
}
/*
* Read with byte stream
* */
@Test
public void run2() throws Exception {
    //1. Create Properties object (ready to read data)
    Properties p = new Properties();
    //2. To create an input stream, the read file extension must be:. properties
    FileInputStream fis = new FileInputStream("Byte stream.properties");
    //3. Read load / read
    p.load(fis);
    System.out.println(p);
    //4, Guan Liu
    fis.close();
}

/*
*   Write in byte stream
*  */
@Test
public void run1() throws Exception {
    //1. Create the Properties object and save the data
    Properties p = new Properties();
    p.setProperty("name","Eldest brother");
    p.setProperty("sex","Pure men");
    //2. Create output stream object extension must be:. properties
    FileOutputStream fos = new FileOutputStream("Byte stream.properties");
    //3. Write out file: store store
    p.store(fos,"This is the big brother's message");
    //4, Guan Liu
    fos.close();
}

 

 

Write in character stream:

/*
* Read with character stream
* */
@Test
public void run3() throws Exception {
    //1. Create Properties object (ready to read data)
    Properties p = new Properties();
    //2. To create an input stream, the read file extension must be:. properties
    FileReader fr = new FileReader("Character stream.properties");
    //3. Read load / read
    p.load(fr);
    System.out.println(p);
    //4, Guan Liu
    fr.close();
}
/*
* Read with byte stream
* */
@Test
public void run2() throws Exception {
    //1. Create Properties object (ready to read data)
    Properties p = new Properties();
    //2. To create an input stream, the read file extension must be:. properties
    FileInputStream fis = new FileInputStream("Character stream.properties");
    //3. Read load / read
    p.load(fis);
    System.out.println(p);
    //4, Guan Liu
    fis.close();
}

/*
*   Write in character stream
*  */
@Test
public void run1() throws Exception {
    //1. Create the Properties object and save the data
    Properties p = new Properties();
    p.setProperty("name","Eldest brother");
    p.setProperty("sex","Pure men");
    //2. Create output stream object extension must be:. properties
    FileWriter fw = new FileWriter("Character stream.properties");
    //3. Write out file: store store
    p.store(fw,"This is the big brother's message");
    //4, Guan Liu
    fw.close();
}

 

 

A file written out by a byte stream that can be read by either a byte stream or a character stream

The file written out by character stream can only be read by character stream (byte stream scrambling)

 

Recommendation: use byte stream to read and write

 

 

 

6, IDEA creates Properties file

 

 

 

 

Today's summary:

Properties: a collection of persisted data. (HashMap)   Persistence: save memory data to hard disk.   Both Key and value are String strings   setProperties(key,value);     map.put(key,value) getProperties(key); map.get(key) stringPropertyNames(); map.keySet();     Output stream: extension.properties Store (output stream object, description information);   Input stream Load (input stream object)   Byte stream: write, any stream can read [suggestions] Character stream: write out, only character stream

 

 

 

 

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