Java anonymous inner class passing value-javaTutorial-php.cn

Java anonymous inner class passing value

高洛峰

Release： 2016-12-15 13:01:08

Original

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In Nutz, there are a lot of situations where anonymous internal classes need to be used. Many children are confused about passing values, so I will explain here

Incoming:

//匿名内部类,只能访问final的本地变量及方法参数 
public void addUser(final String name, String passwd, final String userType) { 
    User user = null; 
    if ("admin".equal(userType)) 
        user = new AdminUser(name, passwd); //仅作演示. 
    else 
        user = new User(name, passwd); 
    final User _user = user; //因为user变量不能设置为final,所以需要新加一个变量来中转 
    Trans.run(new Atom(){ 
        public void run() { 
            dao.insert(_user); 
            if (log.isDebugEnable()) 
                log.debugf("Add user id=%d, name=%s , type=%s", _user.getId(), name, userType); 
        } 
    }); 
}

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Outgoing (getting method return value, etc.):

Method 1 – The object array method uses a final Object object array to store the required values

public long countUser(final String userType) { 
    final Object[] objs = new Object[1]; 
    Trans.run(new Atom(){ 
        public void run() { 
            objs[0] = dao.count(User.class, Cnd.where(&#39;userType&#39;, &#39;=&#39;, userType)); 
        } 
    }); 
    return ((Number)objs[0]).longValue(); 
}

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Method 2 – The ThreadLocal method uses a ThreadLocal to store the results. This ThreadLocal can be static and used by the entire app.

private static final ThreadLocal re = new ThreadLocal(); //自行补上泛型Object 
public long countUser(final String userType) { 
    Trans.run(new Atom(){ 
        public void run() { 
            re.set(dao.count(User.class, Cnd.where(&#39;userType&#39;, &#39;=&#39;, userType))); 
        } 
    }); 
    return ((Number)re.get()).longValue(); //严谨一点的话,应该将ThreadLocal置空 
}

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Method 3 – Molecule method The Molecule class is Nutz’s built-in abstract class, which implements the Runnable and Atom interfaces and adds two methods to get/set values.

public long countUser(final String userType) { 
    Molecule mole = new Molecule() { //需要自行补齐泛型 
        public void run() { 
            setObj(dao.count(User.class, Cnd.where(&#39;userType&#39;, &#39;=&#39;, userType))); 
        } 
    }; 
    Trans.run(mole); 
    return ((Number)mole.getObj()).longValue(); 
}

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