Class Tables


  • public class Tables
    extends java.lang.Object
    Utility class for miscellaneous table-related functionality.
    • Field Detail

      • NULL_VALUE_INFO

        public static final ValueInfo NULL_VALUE_INFO
        ValueInfo which may be used as part of a column's metadata to indicate a special value (preferably a Number that should be interpreted as a null (blank). This should only be used on nullable columns, and really only on ones with a contentClass which is an integer (or possibly boolean) type; for other types, there is usually a value which can conventionally be understood to mean blank. Note this is here as a standard key to use when software components wish to communicate this information; the table system does not guarantee to honour instances of this value in a column's auxiliary data. It is the job of a StarTable instance to ensure that a null is returned from the table interrogation methods if that is what is meant.
      • UBYTE_FLAG_INFO

        public static final ValueInfo UBYTE_FLAG_INFO
        ValueInfo which may be used as part of a column's auxiliary metadata to indicate that the column's data represents, and can be serialised as, unsigned byte values. If so, the value is set to Boolean.TRUE (other values are treated as if absent). Data representing unsigned byte values will normally be represented within STIL by Short (16-bit integer) signed values, since there is no unsigned byte type in java. However, this flag may be used to indicate that the values can be serialised to unsigned-byte-capable output formats (for instance FITS and VOTable) using an unsigned byte serialisation. This annotation will normally only be honoured if the data type of the column is (scalar or array) short integer (16-bit) values. Some care should be exercised in applying this flag or (especially) modifying values in columns it applies to, that the actual column value range remains in the unsigned byte data range (0..255), since otherwise problems will result if it is serialised.
      • RA_INFO

        public static final DefaultValueInfo RA_INFO
        ValueInfo representing Right Ascension. The units are radians and it is non-nullable.
      • DEC_INFO

        public static final DefaultValueInfo DEC_INFO
        ValueInfo representing Declination. The units are radians and it is non-nullable.
    • Constructor Detail

      • Tables

        public Tables()
    • Method Detail

      • randomTable

        public static StarTable randomTable​(StarTable startab)
                                     throws java.io.IOException
        Returns a table based on a given table and guaranteed to have random access. If the original table stab has random access then it is returned, otherwise a new random access table is built using its data.

        This convenience method is equivalent to calling StoragePolicy.getDefaultPolicy().randomTable(startab).

        Parameters:
        startab - original table
        Returns:
        a table with the same data as startab and with isRandom()==true
        Throws:
        java.io.IOException
      • getColumnInfos

        public static ColumnInfo[] getColumnInfos​(StarTable startab)
        Convenience method to return an array of all the column headers in a given table. Modifying this array will not affect the table.
        Parameters:
        startab - the table being enquired about
        Returns:
        an array of all the column headers
      • deleteColumn

        public static StarTable deleteColumn​(StarTable startab,
                                             int icol)
        Returns a table equivalent to the original but with a given column deleted. The result may or may not be the same object as the input table.
        Parameters:
        startab - the table from which to delete a column
        icol - the index of the column to be deleted
        Throws:
        java.lang.IndexOutOfBoundsException - if startab has no column at icol
      • streamStarTable

        public static void streamStarTable​(StarTable source,
                                           TableSink sink)
                                    throws java.io.IOException
        Copies the data and metadata from a StarTable into a table sink. This method is supplied for convenience; its implementation is very straightforward.
        Parameters:
        source - table to be copied
        sink - table destination
        Throws:
        java.io.IOException
      • getDefaultRowSplittable

        public static RowSplittable getDefaultRowSplittable​(StarTable table)
                                                     throws java.io.IOException
        Returns a RowSplittable object with generic characteristics for a given table. For a random-access table the splitting will be based on RowAccess objects, and for a non-random table it will not be capable of splits.
        Parameters:
        table - table
        Returns:
        splittable for potentially parallel iteration over rows
        Throws:
        java.io.IOException
      • checkTable

        public static void checkTable​(StarTable table)
                               throws java.io.IOException
        Diagnostic method which tests the invariants of a StarTable. This method returns no value, and throws an exception if a table is illegal in some way. If this method throws an exception when called on a given StarTable, that table is deemed to be bad in some way (buggy implementation or I/O trouble during access). This method is provided for convenience and diagnostics because there are a number of ways, some of them subtle, in which a StarTable can fail to fulfil its general contract.

        That a table passes this test does not guarantee that the table has no bugs. This method should not generally be used in production code, since it may be expensive in time and/or memory.

        Parameters:
        table - table to test
        Throws:
        java.lang.AssertionError - if an invariant is violated
        java.io.IOException - if there is an I/O error
      • checksumData

        public static int checksumData​(StarTable table)
                                throws java.io.IOException
        Returns a checksum of all the cell data in a given table. Currently, the Adler32 checksum is used.
        Parameters:
        table - table to checksum
        Returns:
        checksum value
        Throws:
        java.io.IOException
      • checksumData

        public static long checksumData​(RowSequence rseq,
                                        java.util.zip.Checksum checksum)
                                 throws java.io.IOException
        Feeds the data from a row sequence to a supplied checksum accumulator.
        Parameters:
        rseq - row sequence containing data
        checksum - checksum accumulator
        Returns:
        number of rows checksummed (note this is not the checksum value)
        Throws:
        java.io.IOException
      • isBlank

        public static boolean isBlank​(java.lang.Object value)
        Indicates whether a given value is conventionally regarded as a blank value. For most objects this is equivalent to testing whether it is equall to null, but some classes have additional non-null values which count as blanks, for instance zero-length Strings and floating Not-A-Number values.
        Parameters:
        value - value to test
        Returns:
        true iff value counts as a blank value
      • collapseWhitespace

        public static java.lang.String collapseWhitespace​(java.lang.String txt)
        Collapses whitespace in a string. This normalises the text in the sense of the XML Schema facet whitespace='collapse': leading and trailing whitespace is removed, and any other run of whitespace is replaced by a single space character.
        Parameters:
        txt - input string (may be null)
        Returns:
        string with whitespaces collapsed
      • singleTableSequence

        public static TableSequence singleTableSequence​(StarTable table)
        Convenience method to construct a TableSequence for a single table.
        Parameters:
        table - table
        Returns:
        table sequence with just one element
      • arrayTableSequence

        public static TableSequence arrayTableSequence​(StarTable[] tables)
        Convenience method to construct a TableSequence for a supplied array of tables.
        Parameters:
        tables - table array
        Returns:
        table sequence containing input tables
      • tableArray

        public static StarTable[] tableArray​(TableSequence tseq)
                                      throws java.io.IOException
        Convenience method to construct an array of StarTables from a TableSequence.
        Parameters:
        tseq - table sequence
        Returns:
        array containing tables from sequence
        Throws:
        java.io.IOException
      • sortTable

        public static StarTable sortTable​(StarTable table,
                                          int[] colIndices,
                                          boolean up,
                                          boolean nullsLast)
                                   throws java.io.IOException
        Returns a sorted version of a table. The sorting is done on the values of one or more columns, as specified by the colIndices argument; the first element is the primary sort key, but in case of a tie the second element is used, and so on. The original table is not affected. The natural comparison order of the values in the table is used, and blank values may be ranked at the start or end of the collation order.
        Parameters:
        table - table to sort - must be random access
        colIndices - indices of the columns which are to act as sort keys; first element is primary key etc
        up - true for sorting into ascending order, false for descending order
        nullsLast - true if blank values should be considered last in the collation order, false if they should be considered first
        Returns:
        a table with the same rows as table but in an order determined by the other arguments
        Throws:
        java.io.IOException - if table.isRandom is not true
      • tableToString

        public static java.lang.String tableToString​(StarTable table,
                                                     java.lang.String ofmt)
        Returns the contents of a table as a string. Only intended for small tables, for instance during debugging.
        Parameters:
        table - input table
        ofmt - output format specifier, or null for plain text output
        Returns:
        stringified table
      • checkedLongToInt

        public static int checkedLongToInt​(long lval)
        Convenience method to get an int value from a long. If the supplied long integer lval is out of the range which can be represented in an int, then unlike a typecast, this method will throw an IllegalArgumentException.
        Parameters:
        lval - the long value to convert
        Returns:
        an int value which has the same value as lval
        Throws:
        java.lang.IllegalArgumentException - if the conversion cannot be done
      • assertLongToInt

        public static int assertLongToInt​(long lval)
        Casts a long to an int, with an assertion that no truncation occurs.
        Parameters:
        lval - long value, asserted to be in the range Integer.MIN_VALUE..Integer.MAX_VALUE
        Returns:
        truncated version of lval
      • getElementLabels

        public static java.lang.String[] getElementLabels​(int[] shape)
        Returns an array of strings suitable as labels or label suffixes for elements of an array as returned by ValueInfo.getShape(). If the given shape cannot be decomposed into a fixed size array, returns null.
        Parameters:
        shape - vector giving dimensions of an array value
        Returns:
        array with one element for each element of the array values (in their natural order), or null for non-array shapes
      • getXtype

        @Deprecated
        public static java.lang.String getXtype​(ValueInfo info)
        Deprecated.
        Returns the extended type value associated with a given metadata item. The XType corresponds to the xtype attribute of the VOTable format. Other table formats may or may not be able to represent it.
        Parameters:
        info - metadata item
        Returns:
        xtype string, or null if none is available
      • setDescribedValue

        public static void setDescribedValue​(java.util.Collection<DescribedValue> dvals,
                                             DescribedValue dval)
        Utility method to update a list of DescribedValues with a new entry. If an item with the same name as the new entry already exists, it is removed.
        Parameters:
        dvals - list to modify
        dval - new entry to add
      • getDescribedValueByName

        public static DescribedValue getDescribedValueByName​(java.util.Collection<DescribedValue> dvals,
                                                             java.lang.String name)
        Utility method to locate an element in a list of DescribedValue given the name of its ValueInfo member.
        Parameters:
        dvals - list to query
        name - required value of name
        Returns:
        element of dvals for which getInfo().getName() matches name
      • getAuxDatumValue

        public static <T> T getAuxDatumValue​(ValueInfo info,
                                             ValueInfo auxKey,
                                             java.lang.Class<T> auxClazz)
        Utility method to return an auxiliary metadata item from a ValueInfo.
        Parameters:
        info - metadata item
        auxKey - info identifying aux metadata entry in info
        auxClazz - required result type
        Returns:
        typed aux metadata item requested, or null if it doesn't exist or has the wrong type
      • getTypedValue

        public static <T> T getTypedValue​(DescribedValue dval,
                                          java.lang.Class<T> clazz)
        Utility method to get a typed value from a, possibly null, described value.
        Parameters:
        dval - described value, or null
        clazz - required return type
        Returns:
        typed value of dval, or null if dval is null, or if dval's value has the wrong type
      • getValue

        public static java.lang.Object getValue​(java.util.Collection<DescribedValue> dvals,
                                                ValueInfo info)
        Returns the value from a list of DescribedValue objects which corresponds to a given info key. If the key is not represented in the list, or if its value is null, then null is returned.
        Parameters:
        dvals - list of DescribedValue objects
        info - key giving the value you want
        Returns:
        matching value
      • fixColumns

        public static void fixColumns​(ColumnInfo[][] infoLists,
                                      JoinFixAction[] fixActs)
        Performs deduplication of column names for N lists of column metadata objects that will be combined to form a new table. The arguments are matched arrays; each list of column infos has a corresponding renaming policy. The ColumnInfo objects are renamed in place as required.
        Parameters:
        infoLists - array of N arrays of column metadata objects
        fixActs - array of N policies for renaming columns