[Solved] An external frame of zeroes

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An external frame means that you have to add two rows/columns each (left and right/ upper and lower), so you need to increase the size of your new matrix by an additional row and column.
The loops for setting the frame to 0 were fine.
At the last inner loop you set the reduced size of the initial matrix as condition instead of the new one as in the outer loop.

public static char[][] Frame_of_zeros(char[][]a)//builds an external frame of zeroes
{
    char[][]c3=new char[a.length+2][a[0].length+2];
    for(int i=0,j=0;i<c3.length;i++)//left column is composed of zeroes
    {
        c3[i][j]='0';
    }
    for(int j=0,i=0;j<c3[0].length;j++)//upper row of zeroes
    {
        c3[i][j]='0';
    }
    for(int i=c3.length-1,j=0;j<c3[0].length;j++)//most lower row composed of zeroes
    {
        c3[i][j]='0';
    }
    for(int i=0,j=c3[0].length-1;i<c3.length;i++)//right column is composed of zeroes
    {
        c3[i][j]='0';
    }

    for(int i=1,k=0;i<c3.length-1 && k<a.length;i++,k++)//i for the modified and k is the original
    {
        for(int j=1,l=0;j<c3[0].length-1 && l<a[0].length;j++,l++)//j for the modified and l is the original
        {
            c3[i][j]=a[k][l];
        }
    }
    return c3;
}

solved An external frame of zeroes