Effective Java 1

 1 public class Builder_Pattern {
 2     private final int p1;
 3     private final int p2;
 4     private final int p3;
 5     private final int p4;
 6 
 7     public static class Builder{
 8         private final int p1;
 9         private final int p2;
10 
11         private int p3=0;
12         private int p4=0;
13 
14         public Builder(int p1,int p2){
15             this.p1=p1;
16             this.p2=p2;
17         }
18         public Builder p3(int val){
19             p3=val; return this;
20         }
21         public Builder p4(int val){
22             p4=val; return this;
23         }
24         public Builder_Pattern build(){
25             return new Builder_Pattern(this);
26         }
27     }
28 
29     private Builder_Pattern(Builder builder){
30         p1=builder.p1;p2=builder.p2;p3=builder.p3;p4=builder.p4;
31     }
32 
33 
34 //Builder_Pattern bp=new Builder_Pattern.Builder(1,2).p3(1).p4(1).build(); 注意 p3 p4返回类型是Builder 可以连续调用！
35 }