【Effective Java】2、构造参数过多的时候

package cn.xf.cp.ch02.item2;

/**
 *
 * 功能：当我们的构造参数有很多，超出可控范围的时候,用build模式 时间：下午8:25:05 文件：NutritionFacts.java
 *
 * @author Administrator
 *
 */
public class NutritionFacts
{
    private final int    param1;
    private final int    param2;
    private final int    param3;
    private final int    param4;
    private final int    param5;
    private final int    param6;
    private final int    param7;

    public static void main(String[] args)
    {
        // 初始化NutritionFacts
        NutritionFacts test = new NutritionFacts.Builder(1, 2).param3(3).param4(4).param5(5).param6(6).param7(7)
                .build();
    }

    private NutritionFacts(Builder build)
    {
        param1 = build.param1;
        param2 = build.param2;
        param3 = build.param3;
        param4 = build.param4;
        param5 = build.param5;
        param6 = build.param6;
        param7 = build.param7;
    }

    public static class Builder
    {
        private final int    param1;
        private final int    param2;
        private int            param3    = 0;
        private int            param4    = 0;
        private int            param5    = 0;
        private int            param6    = 0;
        private int            param7    = 0;

        public Builder(int param1, int param2)
        {
            this.param1 = param1;
            this.param2 = param2;
        }

        public Builder param3(int val)
        {
            param3 = val;
            return this;
        }

        public Builder param4(int val)
        {
            param3 = val;
            return this;
        }

        public Builder param5(int val)
        {
            param3 = val;
            return this;
        }

        public Builder param6(int val)
        {
            param3 = val;
            return this;
        }

        public Builder param7(int val)
        {
            param3 = val;
            return this;
        }

        public NutritionFacts build()
        {
            return new NutritionFacts(this);
        }
    }
}