1. 餓漢式

/**
 * 單列設(shè)計模式 餓漢式
 * @author chenPeng
 * @version 1.0.0
 * @ClassName PropertiesHolder.java
 * @Description TODO
 * @createTime 2019年01月28日 19:23:00
 */
public class PropertiesHolderHunger {
    private static Properties pros = new Properties();
    static {
        try {
            pros.load(PropertiesHolderHunger.class.getClassLoader().getResourceAsStream(
                    "config.properties"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static Properties getPros() {
        return pros;
    }

    @Test
    public void proTest() throws IOException {
        Properties pros = getPros();
        String temp = pros.getProperty("LOG_SOURCE_DIR");
        System.out.println(temp);
    }
}

懶漢式

/**
 * 單列模式：懶漢式——并考慮線程安全
 * @author chenPeng
 * @version 1.0.0
 * @ClassName PropertiesHolderLaze.java
 * @Description TODO
 * @createTime 2019年01月28日 19:47:00
 */
public class PropertiesHolderLaze {
    private static Properties pros = null;

    public static Properties getPros() throws IOException {
        if (pros==null){
            synchronized (PropertiesHolderLaze.class){
                if (pros==null){
                    pros = new Properties();
                    pros.load(PropertiesHolderLaze.class.getClassLoader().getResourceAsStream(
                            "config.properties"));
                }
            }
        }
        return pros;
    }
}

解釋

1. 獲取配置文件的輸入流

PropertiesHolderLaze.class.getClassLoader().getResourceAsStream("config.properties")

2. synchronized為鎖