java - 如何在java中格式化时隔离括号

Question

我想创建 SQL 更新查询。这里我创建了请求的 SET 部分:

String placeholders = "{0} = {1}";
StringBuilder newvalues = new StringBuilder();
for( String key : fields.keySet() ) {
    newvalues.append(MessageFormat.format(placeholders, key, fields.get(key)));
}

这里字段是Map对象。 SET中所有值都没有''括号的问题:

SET column1 = value1, column2 = value2

值可以类似于“1.234.2344”。这就是为什么我需要以某种方式添加 ' ' 到占位符。但这样做:

String placeholders = "{0} = '{1}'";

或

String placeholders = "{0} = \'{1}\'";

不会将“”添加到字符串中。相反，format 函数让 {1} 保持原样(((如何将“”添加到占位符模板中，以便 format 可以对其进行格式化)

Answer 1

来自java文档MessageFormat java doc :

Within a String, a pair of single quotes can be used to quote any arbitrary characters except single quotes. For example, pattern string "'{0}'" represents string "{0}", not a FormatElement. A single quote itself must be represented by doubled single quotes ''

所以你需要这样做

字符串占位符 = "{0} = ''{1}''";