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Add method to wrap list of maps as a table
This will be useful in script languages like Groovy, so that (small) tables can be written succinctly: table = Tables.wrap([ ["Town": "Shanghai", "Population": 24_256_800], ["Town": "Karachi", "Population": 23_500_000], ["Town": "Beijing", "Population": 21_516_000], ["Town": "Sao Paolo", "Population": 21_292_893], ])
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‎src/main/java/org/scijava/table/Tables.java‎

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package org.scijava.table;
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import java.util.Collection;
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import java.util.List;
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import java.util.Map;
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import java.util.Objects;
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/**
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* Utility methods for constructing tables.
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*
@@ -41,6 +46,99 @@ private Tables() {
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// NB: Prevent instantiation of utility class.
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}
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/**
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* Creates a table wrapping a list of maps. Each map is one row of the table.
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* Map keys are column names; map values are cell data.
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* <p>
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* Note that columns are inferred from the first map/row of the table, not
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* unioned across all rows.
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* </p>
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*
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* @param data The data to wrap. Each list element is a row; maps go from
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* column name to data.
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* @param rowHeaders List of row header labels. Pass null for no row headers.
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* @return A {@link Table} object wrapping the data structure.
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*/
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public static <T> Table<Column<T>, T> wrap(
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final List<? extends Map<?, ? extends T>> data, final List<String> rowHeaders)
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{
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if (data.isEmpty()) throw new IllegalArgumentException("Cannot wrap an empty list");
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return new ReadOnlyTable<T>() {
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@Override
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public int getRowCount() {
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return data.size();
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}
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@Override
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public String getRowHeader(final int row) {
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if (rowHeaders == null || rowHeaders.size() < row) return null;
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return rowHeaders.get(row);
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}
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@Override
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public int size() {
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return data.get(0).size();
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}
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@Override
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public Column<T> get(final int col) {
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class ColumnAccessor implements ReadOnlyColumn<T> {
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private final Object tableData = data;
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private boolean initialized;
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private String colHeader;
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@Override
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public String getHeader() {
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if (!initialized) {
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int c = 0;
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for (final Object key : data.get(0).keySet()) {
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if (col == c++) {
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colHeader = key == null ? "<null>" : key.toString();
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break;
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}
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}
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initialized = true;
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}
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return colHeader;
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}
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@Override
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public int size() {
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return data.size();
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}
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@Override
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public Class<T> getType() {
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// TODO: Consider whether this is terrible.
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throw new UnsupportedOperationException();
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}
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@Override
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public T get(final int index) {
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return data.get(index).get(getHeader());
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}
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@Override
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public int hashCode() {
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return getHeader().hashCode();
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}
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@Override
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public boolean equals(final Object obj) {
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if (!(obj instanceof ColumnAccessor)) return false;
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final ColumnAccessor other = ((ColumnAccessor) obj);
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if (data != other.tableData) return false;
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return Objects.equals(getHeader(), other.getHeader());
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}
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}
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return new ColumnAccessor();
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}
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};
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}
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// -- Internal methods --
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/**
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throw new IndexOutOfBoundsException("Invalid " + name + "s: " + index +
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" - " + last);
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}
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private static UnsupportedOperationException readOnlyException() {
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return new UnsupportedOperationException("Wrapped table is read-only");
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}
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// -- Helper classes --
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/** Read-only version of a {@link Table}. */
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private static interface ReadOnlyTable<T> extends Table<Column<T>, T> {
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@Override
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default void setColumnCount(final int colCount) {
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throw readOnlyException();
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}
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@Override
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default List<Column<T>> insertColumns(final int col, final int count) {
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throw readOnlyException();
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}
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@Override
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default void setRowCount(final int rowCount) {
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throw readOnlyException();
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}
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@Override
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default void removeRows(int row, int count) {
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throw readOnlyException();
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}
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@Override
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default void setRowHeader(int row, String header) {
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throw readOnlyException();
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}
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@Override
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default void set(String colHeader, int row, T value) {
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throw readOnlyException();
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}
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@Override
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default boolean add(final Column<T> column) {
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throw readOnlyException();
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}
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@Override
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default boolean remove(final Object column) {
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throw readOnlyException();
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}
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@Override
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default boolean addAll(Collection<? extends Column<T>> c) {
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throw readOnlyException();
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}
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@Override
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default boolean addAll(int col, Collection<? extends Column<T>> c) {
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throw readOnlyException();
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}
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@Override
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default boolean removeAll(Collection<?> c) {
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throw readOnlyException();
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}
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@Override
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default boolean retainAll(Collection<?> c) {
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throw readOnlyException();
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}
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@Override
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default void clear() {
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throw readOnlyException();
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}
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@Override
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default Column<T> set(int col, Column<T> column) {
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throw readOnlyException();
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}
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@Override
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default void add(int col, Column<T> column) {
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throw readOnlyException();
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}
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@Override
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default Column<T> remove(int col) {
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throw readOnlyException();
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}
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}
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/** Read-only version of a {@link Column}. */
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private static interface ReadOnlyColumn<T> extends Column<T> {
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@Override
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default boolean add(final T e) {
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throw readOnlyException();
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}
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@Override
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default boolean remove(Object o) {
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throw readOnlyException();
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}
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@Override
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default boolean addAll(Collection<? extends T> c) {
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throw readOnlyException();
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}
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@Override
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default boolean addAll(int index, Collection<? extends T> c) {
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throw readOnlyException();
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}
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@Override
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default boolean removeAll(Collection<?> c) {
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throw readOnlyException();
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}
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@Override
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default boolean retainAll(Collection<?> c) {
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throw readOnlyException();
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}
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@Override
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default void clear() {
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throw readOnlyException();
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}
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@Override
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default T set(int index, T element) {
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throw readOnlyException();
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}
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@Override
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default void add(int index, T element) {
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throw readOnlyException();
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}
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@Override
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default T remove(int index) {
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throw readOnlyException();
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}
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@Override
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default void setHeader(String header) {
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throw readOnlyException();
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}
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@Override
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default void setSize(int size) {
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throw readOnlyException();
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}
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}
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}

‎src/test/java/org/scijava/table/TablesTest.java‎

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/*
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* #%L
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* Table structures for SciJava.
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* %%
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* Copyright (C) 2012 - 2018 Board of Regents of the University of
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* Wisconsin-Madison, and Friedrich Miescher Institute for Biomedical Research.
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* %%
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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* #L%
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*/
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package org.scijava.table;
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import static org.junit.Assert.assertEquals;
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import java.util.Arrays;
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import java.util.LinkedHashMap;
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import java.util.List;
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import java.util.Map;
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import org.junit.Test;
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/**
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* Tests {@link Tables}.
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*
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* @author Curtis Rueden
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*/
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public class TablesTest {
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@Test
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public void testWrap() {
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final List<Map<Object, Object>> towns = Arrays.asList( //
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map("Town", "Shanghai", "Population", 24_256_800), //
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map("Town", "Karachi", "Population", 23_500_000), //
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map("Town", "Beijing", "Population", 21_516_000), //
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map("Town", "Sao Paolo", "Population", 21_292_893));
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final List<String> rowHeaders = Arrays.asList("A", "B", "C", "D");
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final Table<Column<Object>, Object> table = Tables.wrap(towns, rowHeaders);
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// check table dimensions
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assertEquals(2, table.size());
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assertEquals(2, table.getColumnCount());
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assertEquals(4, table.getRowCount());
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// check row headers
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for (int r = 0; r < rowHeaders.size(); r++)
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assertEquals(rowHeaders.get(r), table.getRowHeader(r));
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// check direct data access
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assertEquals("Shanghai", table.get(0, 0));
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assertEquals("Karachi", table.get(0, 1));
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assertEquals("Beijing", table.get(0, 2));
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assertEquals("Sao Paolo", table.get(0, 3));
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assertEquals(24_256_800, table.get(1, 0));
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assertEquals(23_500_000, table.get(1, 1));
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assertEquals(21_516_000, table.get(1, 2));
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assertEquals(21_292_893, table.get(1, 3));
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// check first column
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assertEquals("Town", table.getColumnHeader(0));
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final Column<Object> townColumn = table.get("Town");
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assertEquals(4, townColumn.size());
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assertEquals("Shanghai", townColumn.get(0));
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assertEquals("Karachi", townColumn.get(1));
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assertEquals("Beijing", townColumn.get(2));
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assertEquals("Sao Paolo", townColumn.get(3));
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assertEquals(townColumn, table.get(0));
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// check second column
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assertEquals("Population", table.getColumnHeader(1));
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final Column<Object> popColumn = table.get("Population");
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assertEquals(4, popColumn.size());
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assertEquals(24_256_800, popColumn.get(0));
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assertEquals(23_500_000, popColumn.get(1));
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assertEquals(21_516_000, popColumn.get(2));
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assertEquals(21_292_893, popColumn.get(3));
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assertEquals(popColumn, table.get(1));
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}
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private Map<Object, Object> map(final Object... kv) {
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final LinkedHashMap<Object, Object> map = new LinkedHashMap<>();
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for (int i = 0; i < kv.length; i += 2)
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map.put(kv[i], kv[i + 1]);
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return map;
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}
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}

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