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Copy pathJsonUtils.java
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220 lines (204 loc) · 7.29 KB
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package com.textparser;
import java.util.*;
public class JsonUtils {
public static Object parseJson(String json) {
return new Parser(json).parse();
}
private static class Parser {
private final String src;
private int pos = 0;
public Parser(String src) {
this.src = src;
}
public Object parse() {
skipWhitespace();
Object value = parseValue();
skipWhitespace();
return value;
}
private Object parseValue() {
skipWhitespace();
if (pos >= src.length()) {
throw new RuntimeException("Unexpected end of JSON input");
}
char ch = src.charAt(pos);
if (ch == '{') {
return parseObject();
} else if (ch == '[') {
return parseArray();
} else if (ch == '"') {
return parseString();
} else if (ch == 't' || ch == 'f') {
return parseBoolean();
} else if (ch == 'n') {
return parseNull();
} else if (ch == '-' || (ch >= '0' && ch <= '9')) {
return parseNumber();
} else {
throw new RuntimeException("Unexpected character in JSON: '" + ch + "' at position " + pos);
}
}
@SuppressWarnings("unchecked")
private Map<String, Object> parseObject() {
Map<String, Object> map = new LinkedHashMap<>();
expect('{');
skipWhitespace();
if (peek() == '}') {
expect('}');
return map;
}
while (true) {
skipWhitespace();
String key = parseString();
skipWhitespace();
expect(':');
Object val = parseValue();
map.put(key, val);
skipWhitespace();
char c = peek();
if (c == '}') {
expect('}');
break;
} else if (c == ',') {
expect(',');
} else {
throw new RuntimeException("Expected ',' or '}' in object at position " + pos);
}
}
return map;
}
private List<Object> parseArray() {
List<Object> list = new ArrayList<>();
expect('[');
skipWhitespace();
if (peek() == ']') {
expect(']');
return list;
}
while (true) {
Object val = parseValue();
list.add(val);
skipWhitespace();
char c = peek();
if (c == ']') {
expect(']');
break;
} else if (c == ',') {
expect(',');
} else {
throw new RuntimeException("Expected ',' or ']' in array at position " + pos);
}
}
return list;
}
private String parseString() {
expect('"');
StringBuilder sb = new StringBuilder();
while (pos < src.length()) {
char c = src.charAt(pos++);
if (c == '"') {
return sb.toString();
} else if (c == '\\') {
if (pos >= src.length()) {
throw new RuntimeException("Unterminated escape sequence in string");
}
char esc = src.charAt(pos++);
switch (esc) {
case '"' -> sb.append('"');
case '\\' -> sb.append('\\');
case '/' -> sb.append('/');
case 'b' -> sb.append('\b');
case 'f' -> sb.append('\f');
case 'n' -> sb.append('\n');
case 'r' -> sb.append('\r');
case 't' -> sb.append('\t');
case 'u' -> {
if (pos + 4 > src.length()) {
throw new RuntimeException("Invalid unicode escape");
}
String hex = src.substring(pos, pos + 4);
pos += 4;
sb.append((char) Integer.parseInt(hex, 16));
}
default -> sb.append(esc);
}
} else {
sb.append(c);
}
}
throw new RuntimeException("Unterminated string literal");
}
private Boolean parseBoolean() {
if (src.startsWith("true", pos)) {
pos += 4;
return Boolean.TRUE;
} else if (src.startsWith("false", pos)) {
pos += 5;
return Boolean.FALSE;
}
throw new RuntimeException("Invalid boolean literal at position " + pos);
}
private Object parseNull() {
if (src.startsWith("null", pos)) {
pos += 4;
return null;
}
throw new RuntimeException("Invalid null literal at position " + pos);
}
private Number parseNumber() {
int start = pos;
if (src.charAt(pos) == '-') pos++;
while (pos < src.length() && Character.isDigit(src.charAt(pos))) {
pos++;
}
boolean isDouble = false;
if (pos < src.length() && src.charAt(pos) == '.') {
isDouble = true;
pos++;
while (pos < src.length() && Character.isDigit(src.charAt(pos))) {
pos++;
}
}
if (pos < src.length() && (src.charAt(pos) == 'e' || src.charAt(pos) == 'E')) {
isDouble = true;
pos++;
if (pos < src.length() && (src.charAt(pos) == '+' || src.charAt(pos) == '-')) {
pos++;
}
while (pos < src.length() && Character.isDigit(src.charAt(pos))) {
pos++;
}
}
String numStr = src.substring(start, pos);
if (isDouble) {
return Double.parseDouble(numStr);
} else {
try {
return Long.parseLong(numStr);
} catch (NumberFormatException e) {
return Double.parseDouble(numStr);
}
}
}
private void skipWhitespace() {
while (pos < src.length()) {
char c = src.charAt(pos);
if (c == ' ' || c == '\t' || c == '\n' || c == '\r') {
pos++;
} else {
break;
}
}
}
private char peek() {
if (pos >= src.length()) return '\0';
return src.charAt(pos);
}
private void expect(char expected) {
if (pos >= src.length() || src.charAt(pos) != expected) {
throw new RuntimeException("Expected '" + expected + "' at position " + pos);
}
pos++;
}
}
}