public class TestSingle {
    // 不想在每个类中重复这段代码--------begin
    private static TestSingle instance = new TestSingle();
    public static TestSingle getInstance() {
        return instance;
    }
    private TestSingle () {
    }
    // 不想在每个类中重复这段代码--------end
}

public class Test {

    private static Map<String, Object> map = new HashMap<String, Object>();
    
    public static Object getSingleObject(String className) throws Exception{
        if(map.get(className)==null){
            Object obj = Class.forName(className).newInstance();
            map.put(className, obj);
            return obj;
        }
        return map.get(className);
    }
    
}