Question

How can we replace a particular string in existing string in Java?

Example:

String param = "aa,bb,cc";
String str = 
  "select column_val from table_name where a = '?' and b = '?' and c = '?'";

now i want replace params with its position like..

String newStr = 
  "select column_val from table_name where a = 'aa' and b = 'bb' and c = 'cc'";

How can we do this? Is there any existing method in stringutil or is there any method to do this?

Answer 1

I suggest you to use StringBuilder. They offer some performance gain in your type of string manipulation, especially if your sql or params are long strings.

Here is an example:

String param = "aa,bb,cc";
String str = 
     "select column_val from table_name where a = '?' and b = '?' and c = '?'";

@Test
public void Substitute(){
    StringBuilder builder=new StringBuilder(str);

    String[] params = param.split(",");
    int position=0;
    for (String paramValue:params){
        position=builder.indexOf("?",position);
        if (position==-1)
            throw new RuntimeException("too parameter values specified.");
        builder.replace(position,position+1,paramValue);
        position++;
    }
    position=str.indexOf("?",position);
    if (position!=-1)
        throw new RuntimeException("Not all parameter specified.");

    Assert.assertEquals(builder.toString(),
          "select column_val from table_name where a = 'aa' and b = 'bb' and c = 'cc'");

}

As others have said, remember to sanitize param values to avoid security issues…