快速上手Java中的Properties集合类

ip=192.168.1.100
user=root
pwd=123456

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Properties01 {
    public static void main(String[] args) {       
        BufferedReader bufferedReader = null;
        try {
            bufferedReader = new BufferedReader(new FileReader("src\\test.properties"));
            String line = "";
            while ((line = bufferedReader.readLine()) !=null){
                String[] split = line.split("=");
                System.out.println(split[0]+"值是:"+split[1]);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                bufferedReader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.io.FileReader;
import java.io.IOException;
import java.util.Properties;

public class Properties02 {
    public static void main(String[] args) {
        //创建Properties对象
        Properties properties = new Properties();
        //加载指定的配置文件
        try {
            properties.load(new FileReader("src\\test.properties"));
            //把键值对显示到控制台
            properties.list(System.out);
            System.out.println("===根据键获取对应的值===");
            System.out.println(properties.getProperty("ip"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.FileWriter;
import java.io.IOException;
import java.util.Properties;

public class Properties03 {
    public static void main(String[] args) {
        Properties properties = new Properties();
        properties.setProperty("charset", "UTF-8");
        properties.setProperty("user", "jack");
        properties.setProperty("pwd", "123456");
        try {
            properties.store(new FileWriter("src\\test.properties"), null);
            //第二个参数，表示注释信息（null表示没有注释）
            System.out.println("保存配置文件成功");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.FileWriter;
import java.io.IOException;
import java.util.Properties;

public class Properties04 {
    public static void main(String[] args) {
        Properties properties = new Properties();
        properties.setProperty("charset", "UTF-8");
        properties.setProperty("user", "jack");
        properties.setProperty("pwd", "123456");

        properties.setProperty("user", "tom");
        properties.setProperty("pwd", "888888");
        try {
            properties.store(new FileWriter("src\\test.properties"), null);
            System.out.println("保存配置文件成功");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

public synchronized V put(K key, V value) {
    // Make sure the value is not null
    if (value == null) {
        throw new NullPointerException();
    }

    // Makes sure the key is not already in the hashtable.
    Entry<?,?> tab[] = table;
    int hash = key.hashCode();
    int index = (hash & 0x7FFFFFFF) % tab.length;
    @SuppressWarnings("unchecked")
    Entry<K,V> entry = (Entry<K,V>)tab[index];
    for(; entry != null ; entry = entry.next) {
        if ((entry.hash == hash) && entry.key.equals(key)) {
            V old = entry.value;
            entry.value = value;
            return old;
        }
    }

    addEntry(hash, key, value, index);
    return null;
}