update: 使用Peekable接口代替原来的PashbackReader

Author: nintha

src/main/java/top/nintha/json/JsonNumber.java

@@ -1,7 +1,5 @@
 package top.nintha.json;
 
-import java.util.HashMap;
-
 public class JsonNumber implements JsonValue {
     private double value = 0.0;
 

src/main/java/top/nintha/json/Parser.java

@@ -1,28 +1,18 @@
 package top.nintha.json;
 
-import java.io.IOException;
-import java.io.PushbackReader;
-import java.io.StringReader;
-
 public class Parser {
     private final Tokenizer tokenizer;
 
     public Parser(String json) {
-        StringReader reader = new StringReader(json);
-        this.tokenizer = new Tokenizer(new PushbackReader(reader));
+        this.tokenizer = new Tokenizer(json);
     }
 
     public JsonValue parse() {
         return parseToken(step());
     }
 
     private Token step() {
-        Token token = null;
-        try {
-            token = tokenizer.next();
-        } catch (IOException e) {
-            throw new RuntimeException(e);
-        }
+        Token token = tokenizer.next();
         if (token == null) {
             throw new RuntimeException("Unexpected end of JSON");
         }

src/main/java/top/nintha/json/TokenType.java

@@ -1,20 +1,18 @@
 package top.nintha.json;
 
-import java.io.IOException;
-import java.io.PushbackReader;
+import top.nintha.json.util.TextCharIterator;
 
 public class Tokenizer {
 
-    private final PushbackReader reader;
+    private final TextCharIterator iterator;
 
-    public Tokenizer(PushbackReader reader) {
-        this.reader = reader;
+    public Tokenizer(String text) {
+        this.iterator = new TextCharIterator(text);
     }
 
-    public Token next() throws IOException {
-        int v;
-        while ((v = reader.read()) != -1) {
-            char c = (char) v;
+    public Token next() {
+        while (iterator.hasNext()) {
+            char c = iterator.next();
             if (Character.isWhitespace(c)) {
                 continue;
             }
@@ -23,7 +21,7 @@ public Token next() throws IOException {
         return null;
     }
 
-    private Token charToToken(char c) throws IOException {
+    private Token charToToken(char c) {
         switch (c) {
             case ',':
                 return new Token.Comma();
@@ -54,12 +52,11 @@ private Token charToToken(char c) throws IOException {
         }
     }
 
-    private String readText(char first) throws IOException {
+    private String readText(char first) {
         StringBuilder sb = new StringBuilder();
         boolean escape = false;
-        int v;
-        while ((v = reader.read()) != -1) {
-            char c = (char) v;
+        while (iterator.hasNext()) {
+            char c = iterator.next();
             if (c == first && !escape) {
                 return sb.toString();
             }
@@ -77,44 +74,42 @@ private String readText(char first) throws IOException {
         return sb.toString();
     }
 
-    private double readNum(char first) throws IOException {
+    private double readNum(char first) {
         StringBuilder sb = new StringBuilder(String.valueOf(first));
         boolean point = false;
-        int v;
-        while ((v = reader.read()) != -1) {
-            char c = (char) v;
+        while (iterator.hasNext()) {
+            char c = iterator.peek();
             // number
             if (c >= '0' && c <= '9') {
                 sb.append(c);
+                iterator.next();
             }
             // point
             else if (c == '.') {
                 if (point) {
-                    reader.unread(c);
                     return Double.parseDouble(sb.toString());
                 } else {
                     point = true;
                     sb.append(c);
+                    iterator.next();
                 }
             }
             // other char
             else {
-                reader.unread(c);
                 return Double.parseDouble(sb.toString());
             }
         }
         return Double.parseDouble(sb.toString());
     }
 
-    private Token readSymbol(char first) throws IOException {
+    private Token readSymbol(char first) {
         StringBuilder sb = new StringBuilder(String.valueOf(first));
-        int v;
-        while ((v = reader.read()) != -1) {
-            char c = (char) v;
+        while (iterator.hasNext()) {
+            char c = iterator.peek();
             if (c >= 'a' && c <= 'z') {
                 sb.append(c);
+                iterator.next();
             } else {
-                reader.unread(c);
                 break;
             }
         }

src/main/java/top/nintha/json/Tokenizer.java

@@ -0,0 +1,8 @@
+package top.nintha.json.util;
+
+public interface Peekable<T> {
+    /**
+     * get an element, but not consume it.
+     */
+    T peek();
+}

src/main/java/top/nintha/json/util/Peekable.java

@@ -0,0 +1,27 @@
+package top.nintha.json.util;
+
+import java.util.Iterator;
+
+public class TextCharIterator implements Peekable<Character>, Iterator<Character> {
+    private final char[] chars;
+    private int readIndex = 0;
+
+    public TextCharIterator(String text) {
+        this.chars = text.toCharArray();
+    }
+
+    @Override
+    public boolean hasNext() {
+        return readIndex < chars.length;
+    }
+
+    @Override
+    public Character next() {
+        return hasNext() ? chars[readIndex++] : null;
+    }
+
+    @Override
+    public Character peek() {
+        return chars[readIndex];
+    }
+}

src/main/java/top/nintha/json/util/TextCharIterator.java

@@ -82,7 +82,5 @@ void parseObject() {
         Assertions.assertEquals(0.0, object.get("number").asNumber());
         Assertions.assertTrue(object.get("array").asJsonArray().isEmpty());
         Assertions.assertEquals("hello", object.get("string").asString());
-
-//        System.out.println(object.toJson());
     }
 }