Builder 模式是一步一步创建复杂对象的创建型模式 ， 它允许用户在不知道内部构建细节的情况下，可以更精细的控制对象的构造流程 。 该模式是为了将构建复杂对象的过程和它的部件解耦，使得构建过程和部件的表示隔离开来 。

简单实现

public class Computer {

    String mBoard ;
    String mDisplay ;
    String mOs ;

    private Computer(){};

    public String getmBoard() {
        return mBoard;
    }

    public Computer setmBoard(String mBoard) {
        this.mBoard = mBoard;
        return this ;
    }

    public String getmDisplay() {
        return mDisplay;
    }

    public Computer setmDisplay(String mDisplay) {
        this.mDisplay = mDisplay;
        return this ;
    }

    public String getmOs() {
        return mOs;
    }

    public Computer setmOs(String mOs) {
        this.mOs = mOs;
        return this ;
    }

    public static class ComputerBuilder {

        private String mBoard = "default board";
        private String mDisplay = "default display" ;
        private String mOs = "default os";

        public Computer create(){
            Computer computer = new Computer() ;
            computer.setmBoard(mBoard).setmDisplay(mDisplay)
                    .setmOs(mOs) ;
            return computer ;
        };

        public String getmBoard() {
            return mBoard;
        }

        public ComputerBuilder setmBoard(String mBoard) {
            this.mBoard = mBoard;
            return this ;
        }

        public String getmDisplay() {
            return mDisplay;
        }

        public ComputerBuilder setmDisplay(String mDisplay) {
            this.mDisplay = mDisplay;
            return this ;
        }

        public String getmOs() {
            return mOs;
        }

        public ComputerBuilder setmOs(String mOs) {
            this.mOs = mOs;
            return this ;
        }

    }
}

客户端调用

public class test {
    Computer computer = new Computer.ComputerBuilder().setmBoard("saumnging")
            .setmOs("mac os").create();
}

android 源码示例 AlertDialog