方法一: public class PropertyConfig { private static class PropertyConfigInstance { private static final PropertyConfig _instance = new PropertyConfig(); } public static PropertyConfig instance() { return PropertyConfigInstance._instance; } public String get(String key, String defaultValue) { String val = get(key); return val == null ? defaultValue : val; } } 用法: String username = PropertyConfig.instance().get("username","test133").trim();
方法二: public class HttpClientRequest { private static final HttpClientRequest INSTANCE_HTTP = new HttpClientRequest(); public static HttpClientRequest instance() { return INSTANCE_HTTP; } public String sendMessageByHTTP(){ ... } } 用法:sendResult=HttpClientRequest.instance().sendMessageByHTTP();