Question

Many classes in the javax.sql package use new String(str) constructor. For example:

public void setCatalogName(int columnIndex, String catalogName) throws SQLException {
    checkColRange(columnIndex);
    if (catalogName != null)
        colInfo[columnIndex].catName = new String(catalogName);
    else
        colInfo[columnIndex].catName = new String("");
}

Or

public void setUsername(String name) {
    if(name == null)
    {
        username = null;
    } else {
        username = new String(name);
    }
}

And many more:

javax.sql.rowset.serial.SerialStruct.SerialStruct(SQLData, Map>)
javax.sql.rowset.serial.SerialStruct.SerialStruct(Struct, Map>)
javax.sql.rowset.RowSetMetaDataImpl.setCatalogName(int, String)
javax.sql.rowset.RowSetMetaDataImpl.setColumnLabel(int, String)
javax.sql.rowset.RowSetMetaDataImpl.setColumnName(int, String)
javax.sql.rowset.RowSetMetaDataImpl.setColumnTypeName(int, String)
javax.sql.rowset.BaseRowSet.setCommand(String)
javax.sql.rowset.BaseRowSet.setDataSourceName(String)
java.text.DateFormatSymbols.setLocalPatternChars(String)
javax.sql.rowset.BaseRowSet.setNull(int, int, String)

What is the purpose of this? Isn’t it creating unnecessary string instances on the heap?

Answer 1

It appears the code has been changed from JDK6 to JDK7 and all instances of new String(str) were removed. So, although Jon Skeet’s suggestion is quite interesting, it was probably a lame piece of code they found and fixed.