Java remove row from multidimensional array

Question

I have an interesting dilemma;

I have a String[][] pulled from a MySQL database. For simplicity, I have printed the contents using Arrays.deepToString(<arrayname>):

[[1, gimley, <sanitised>, <sanitised>, <sanitised>, <sanitised>, 1994-10-11, <sanitised>, 2015-02-20 08:55:36.0], 
[2, Eris, Exotic, <sanitised>, <sanitised> <sanitised> <sanitised>, <sanitised>, 1996-02-15, <sanitised>, 2015-02-24 13:02:00.0], 
[3, Macca, Maccan, <sanitised>, <sanitised>, <sanitised>, 1996-11-11, University, Probably on Destiny, 2015-02-24 13:03:17.0], 
[4, <sanitised>, bacon, standard, <sanitised>, <sanitised>, 1996-03-12, <sanitised> or <sanitised>; depends, 2015-02-26 15:44:28.0]]

My question is: How can I remove one of the rows of the array-of-arrays, and replace the existing database with the contents of a new array-of-arrays? I understand that this is bad practice as I can just update the table directly, but this exercise requires me to do this method.

How did you populate this array in the first place. Or this is existing code? — Chetan Kinger
– Chetan Kinger, Commented Feb 27, 2015 at 11:09
@NeplatnyUdajI have tried converting this array to a List, edit the list then re-compile the list as a new String[][], but I cannot wrap my head around it. I basically want to remove a specific row by name, when the corresponding name is typed — Michael Wiggins
– Michael Wiggins, Commented Feb 27, 2015 at 11:17
@bot this is populated via a method which fills a blank String[][] with contents from a resultset — Michael Wiggins
– Michael Wiggins, Commented Feb 27, 2015 at 11:18
@MichaelWiggins Why do you want read the entire row before you update it? If you have the freedom to connect to the db, why not write a method that allows you to update a feild in the db for a row? Basically, why do you have to use the method that gives you a 2D array. Why not write your own update method? — Chetan Kinger
– Chetan Kinger, Commented Feb 27, 2015 at 11:21

Andreas · Accepted Answer · 2015-02-27 11:53:33Z

1

do you mean something like this?

public class TestClass {

public static final String[][] removeRow( String[][] source, String rowName ) {
    boolean rowFound = false;
    for ( int i = 0; i < source.length; i++ ) {
        if ( source[ i ][ 0 ].equals( rowName ) ) {
            rowFound = true;
        }
    }
    if ( !rowFound ) {
        return source;
    }

    String[][] result = new String[ source.length - 1][ source[ 0 ].length ];
    int resultIndex = 0;
    for ( int i = 0; i < source.length; i++ ) {
        if ( !source[ i ][ 0 ].equals( rowName ) ) {
            System.arraycopy( source[ i ], 0, result[ resultIndex ], 0, source[ i ].length );
            resultIndex++;
        } 

    }

    return result;
}

@Test
public void test() {
    String[][] source = { 
            { "1", "one", "I", "eins" }, 
            { "2", "two", "II", "zwei" }, 
            { "3", "three", "III", "drei" }, 
            { "4", "four", "IV", "vier" } 
    };

    String[][] result = removeRow( source, "2" );
    assertEquals( "{[1, one, I, eins][3, three, III, drei][4, four, IV, vier]}", toString( result ) );

    result = removeRow( source, "rowNotIn" );
    assertEquals( "{[1, one, I, eins][2, two, II, zwei][3, three, III, drei][4, four, IV, vier]}", toString( result ) );
}

private String toString( String[][] source ) {
    StringBuffer sb = new StringBuffer();
    sb.append( "{" );
    for ( int i = 0; i < source.length; i++ ) {
        sb.append( Arrays.toString( source[ i ] ) );
    }
    sb.append( "}" );
    return sb.toString();
}

}

answered Feb 27, 2015 at 11:53

Andreas

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2 Comments

Michael Wiggins Over a year ago

Sort of, the array is only printed like that, the method used to obtain it is: String[][] dbTable = null; table = conn.createStatement(); String sql = "select * from Profiles"; ResultSet rs = table.executeQuery(sql); rs.last(); int rowNumb = rs.getRow(); ResultSetMetaData rsmd = rs.getMetaData(); int columnS = rsmd.getColumnCount(); rs.beforeFirst(); dbTable= new String[rowNumb][columnS]; int i=0; while(rs.next() && i<rowNumb && rowNumb<100) { for(int j=0;j<columnS;j++) { dbTable[i][j] = rs.getString(j+1); } i++; } return dbTable;

Michael Wiggins Over a year ago

So there are no hard-coded elements for the array, now do you see my issue?

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