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  1. class Json {
  2.  
  3.     public static RootNode create() {
  4.         return new RootNode();
  5.     }
  6.  
  7.     public interface Node<T extends Node<T>> {
  8.         NotRootNode<T> object(String name);
  9.  
  10.         T number(String name, int value);
  11.     }
  12.  
  13.     public static class RootNode extends AbstractNode<RootNode> implements Node<RootNode> {
  14.  
  15.         public RootNode() {
  16.             super(new StringBuilder());
  17.             buf.append("{");
  18.         }
  19.  
  20.         public String build() {
  21.             if (isNotEmpty)
  22.                 buf.setLength(buf.length() - 1);
  23.             buf.append("}");
  24.             return buf.toString();
  25.         }
  26.     }
  27.  
  28.     public static class NotRootNode<P extends Node<P>> extends AbstractNode<NotRootNode<P>> implements Node<NotRootNode<P>> {
  29.  
  30.         private final P parent;
  31.  
  32.         public NotRootNode(StringBuilder buf, P parent) {
  33.             super(buf);
  34.             this.parent = parent;
  35.         }
  36.  
  37.         public P end() {
  38.             if (isNotEmpty)
  39.                 buf.setLength(buf.length() - 1);
  40.             buf.append("},");
  41.             return parent;
  42.         }
  43.     }
  44.  
  45.     private static class AbstractNode<T extends AbstractNode<T>> implements Node<T> {
  46.  
  47.         protected final StringBuilder buf;
  48.         protected boolean isNotEmpty;
  49.  
  50.         public AbstractNode(StringBuilder buf) {
  51.             this.buf = buf;
  52.             this.isNotEmpty = false;
  53.         }
  54.  
  55.         @Override
  56.         public T number(String name, int value) {
  57.             isNotEmpty = true;
  58.             buf.append('\"').append(name).append("\":").append(value).append(',');
  59.             return self();
  60.         }
  61.  
  62.         @Override
  63.         public NotRootNode<T> object(String name) {
  64.             isNotEmpty = true;
  65.             buf.append('\"').append(name).append("\":{");
  66.             return new NotRootNode<>(buf, self());
  67.         }
  68.  
  69.         @SuppressWarnings("unchecked")
  70.         protected T self() {
  71.             return (T) this;
  72.         }
  73.     }
  74. }
  75.  
  76. class Scratch {
  77.     public static void main(String[] args) {
  78.         String str = Json.create()
  79.                 .number("a", 4)
  80.                 .object("b")
  81.                     .number("a", 4)
  82.                     .number("b", 5)
  83.                     .end()
  84.                 .number("c", 5)
  85.                 .build();
  86.         System.out.println(str);
  87.     }
  88. }
Success #stdin #stdout 0.04s 711168KB
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{"a":4,"b":{"a":4,"b":5},"c":5}
https://ideone.com/Kifcv4
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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