Question

我想做类似下面的事情，但它不起作用。我的目标是能够将函数调用嵌套到静态辅助类中以获得更多简洁。

public class StaticHelper {
    public static Class<StaticHelper> doSomthing() {
        System.out.println("I just did something !!");
        return StaticHelper.class;
    }

    public static Class<StaticHelper> doSomthingElse() {
        System.out.println("I just did something else !!");
        return StaticHelper.class;
    }

    public static void main(String[] args) {
        // Does not compiles 
        StaticHelper.doSomthing().doSomthingElse();
    }
}

这可能吗？如果是这样，上面的简单示例将非常有用。

Answer 1

这是不可能的，但使用static imports是。

public class StaticHelper {
    public static void doSomething() {
        System.out.println("I just did something !!");
    }

    public static void doSomethingElse() {
        System.out.println("I just did something else !!");
    }
}

在另一个班级：

import static StaticHelper.*;

class Other {
    public static void main(String[] args) {
        doSomething(); // calls static methods from StaticHelper
        doSomethingElse();
    }
}

或 - 如果方法是逻辑连接的 - 您可以有一个静态工厂方法，其余的是实例方法：

public class StaticHelper {
    public static void beginDoingSomething() {
        // static factory method - you can pass parameters to it if needed
        System.out.println("I just did something !!");
        return new StaticHelper();
        // if needed, initialize the instance with the parameters
    }

    public StaticHelper andDoSomethingElse() {
        // instance method
        // can use the instance parameters (passed to the constructor in the static factory method)
        // or use parameters passed to this method 
        System.out.println("I just did something else !!");
        return this;
        // returns this for chaining
    }
}

在另一个班级：

import static StaticHelper.*;

class Other {
    public static void main(String[] args) {
        doSomething().andDoSomethingElse().andDoSomethingElse();
    }
}

如果你很好地命名方法，你可以形成一个句子：

validate(object).checkEmail().checkName().checkTelephoneStartsWith("+11");

其中validate(object)是一个静态工厂方法，为给定的object构建一个新的验证器实例。

Answer 2

我想你想要这样的东西。

public class StaticHelper {
    private final static StaticHelper INSTANCE = new StaticHelper();

    public static StaticHelper doSomthing(){
        System.out.println("I just did something !!");
        return INSTANCE;
    }

    public static StaticHelper doSomthingElse(){
        System.out.println("I just did something else !!");
        return INSTANCE;
    }

    public static void main(String[] args) {
        StaticHelper.doSomthing().doSomthingElse();
    }
}

或其他方式

public class StaticHelper {
    public static SomeClass doSomthing(){
        return new SomeClass().doSomthing();
    }

    public static SomeClass doSomthingElse(){
        return new SomeClass().doSomthingElse();
    }

    public static void main(String[] args) {
        StaticHelper.doSomthing().doSomthingElse();
    }

    private static class SomeClass {

        public SomeClass doSomthing(){
            System.out.println("I just did something !!");
            return this;
        }

        public SomeClass doSomthingElse(){
            System.out.println("I just did something else !!");
            return this;
        }
    }
}

嵌套调用静态方法

2 个答案: