我正在寻找一个将一个矩形String [] []打印到一个人类可读的表格中的工具，该表格的列长正确。
答案 0 :(得分：22)
如果你想要类似于MySQL命令行客户端输出的东西，你可以使用类似的东西：
import java.io.PrintStream;
import static java.lang.String.format;
import static java.lang.System.out;
public final class PrettyPrinter {
private static final char BORDER_KNOT = '+';
private static final char HORIZONTAL_BORDER = '-';
private static final char VERTICAL_BORDER = '|';
private static final String DEFAULT_AS_NULL = "(NULL)";
private final PrintStream out;
private final String asNull;
public PrettyPrinter(PrintStream out) {
this(out, DEFAULT_AS_NULL);
}
public PrettyPrinter(PrintStream out, String asNull) {
if ( out == null ) {
throw new IllegalArgumentException("No print stream provided");
}
if ( asNull == null ) {
throw new IllegalArgumentException("No NULL-value placeholder provided");
}
this.out = out;
this.asNull = asNull;
}
public void print(String[][] table) {
if ( table == null ) {
throw new IllegalArgumentException("No tabular data provided");
}
if ( table.length == 0 ) {
return;
}
final int[] widths = new int[getMaxColumns(table)];
adjustColumnWidths(table, widths);
printPreparedTable(table, widths, getHorizontalBorder(widths));
}
private void printPreparedTable(String[][] table, int widths[], String horizontalBorder) {
final int lineLength = horizontalBorder.length();
out.println(horizontalBorder);
for ( final String[] row : table ) {
if ( row != null ) {
out.println(getRow(row, widths, lineLength));
out.println(horizontalBorder);
}
}
}
private String getRow(String[] row, int[] widths, int lineLength) {
final StringBuilder builder = new StringBuilder(lineLength).append(VERTICAL_BORDER);
final int maxWidths = widths.length;
for ( int i = 0; i < maxWidths; i++ ) {
builder.append(padRight(getCellValue(safeGet(row, i, null)), widths[i])).append(VERTICAL_BORDER);
}
return builder.toString();
}
private String getHorizontalBorder(int[] widths) {
final StringBuilder builder = new StringBuilder(256);
builder.append(BORDER_KNOT);
for ( final int w : widths ) {
for ( int i = 0; i < w; i++ ) {
builder.append(HORIZONTAL_BORDER);
}
builder.append(BORDER_KNOT);
}
return builder.toString();
}
private int getMaxColumns(String[][] rows) {
int max = 0;
for ( final String[] row : rows ) {
if ( row != null && row.length > max ) {
max = row.length;
}
}
return max;
}
private void adjustColumnWidths(String[][] rows, int[] widths) {
for ( final String[] row : rows ) {
if ( row != null ) {
for ( int c = 0; c < widths.length; c++ ) {
final String cv = getCellValue(safeGet(row, c, asNull));
final int l = cv.length();
if ( widths[c] < l ) {
widths[c] = l;
}
}
}
}
}
private static String padRight(String s, int n) {
return format("%1$-" + n + "s", s);
}
private static String safeGet(String[] array, int index, String defaultValue) {
return index < array.length ? array[index] : defaultValue;
}
private String getCellValue(Object value) {
return value == null ? asNull : value.toString();
}
}
并使用它：
final PrettyPrinter printer = new PrettyPrinter(out);
printer.print(new String[][] {
new String[] {"FIRST NAME", "LAST NAME", "DATE OF BIRTH", "NOTES"},
new String[] {"Joe", "Smith", "November 2, 1972"},
null,
new String[] {"John", "Doe", "April 29, 1970", "Big Brother"},
new String[] {"Jack", null, null, "(yes, no last name)"},
});
上面的代码将产生以下输出：
+----------+---------+----------------+-------------------+
|FIRST NAME|LAST NAME|DATE OF BIRTH |NOTES |
+----------+---------+----------------+-------------------+
|Joe |Smith |November 2, 1972|(NULL) |
+----------+---------+----------------+-------------------+
|John |Doe |April 29, 1970 |Big Brother |
+----------+---------+----------------+-------------------+
|Jack |(NULL) |(NULL) |(yes, no last name)|
+----------+---------+----------------+-------------------+
答案 1 :(得分：9)
我不知道一个可以执行此操作的util库，但您可以使用String.format函数来格式化字符串，因为您想要显示它们。这是我很快写下的一个例子：
String[][] table = {{"Joe", "Bloggs", "18"},
{"Steve", "Jobs", "20"},
{"George", "Cloggs", "21"}};
for(int i=0; i<3; i++){
for(int j=0; j<3; j++){
System.out.print(String.format("%20s", table[i][j]));
}
System.out.println("");
}
这给出了以下输出：
Joe Bloggs 18
Steve Jobs 20
George Cloggs 21
答案 2 :(得分：8)
你可以尝试
System.out.println(Arrays.deepToString(someRectangularStringArray));
这就像没有特定代码一样美妙。
答案 3 :(得分：1)
JakWharton有一个很好的解决方案https://github.com/JakeWharton/flip-tables和格式String []，具有对属性名称和结果集的反射的对象列表。例如
List<Person> people = Arrays.asList(new Person("Foo", "Bar"), new Person("Kit", "Kat"));
System.out.println(FlipTableConverters.fromIterable(people, Person.class));
答案 4 :(得分：0)
由于我偶然发现这个搜索即用型打印机（但不仅仅是针对字符串），我更改了为Lyubomyr Shaydariv编写的the accepted answer代码。由于这可能会增加问题的价值，我将分享它：
import static java.lang.String.format;
public final class PrettyPrinter {
private static final char BORDER_KNOT = '+';
private static final char HORIZONTAL_BORDER = '-';
private static final char VERTICAL_BORDER = '|';
private static final Printer<Object> DEFAULT = new Printer<Object>() {
@Override
public String print(Object obj) {
return obj.toString();
}
};
private static final String DEFAULT_AS_NULL = "(NULL)";
public static String print(Object[][] table) {
return print(table, DEFAULT);
}
public static <T> String print(T[][] table, Printer<T> printer) {
if ( table == null ) {
throw new IllegalArgumentException("No tabular data provided");
}
if ( table.length == 0 ) {
return "";
}
if( printer == null ) {
throw new IllegalArgumentException("No instance of Printer provided");
}
final int[] widths = new int[getMaxColumns(table)];
adjustColumnWidths(table, widths, printer);
return printPreparedTable(table, widths, getHorizontalBorder(widths), printer);
}
private static <T> String printPreparedTable(T[][] table, int widths[], String horizontalBorder, Printer<T> printer) {
final int lineLength = horizontalBorder.length();
StringBuilder sb = new StringBuilder();
sb.append(horizontalBorder);
sb.append('\n');
for ( final T[] row : table ) {
if ( row != null ) {
sb.append(getRow(row, widths, lineLength, printer));
sb.append('\n');
sb.append(horizontalBorder);
sb.append('\n');
}
}
return sb.toString();
}
private static <T> String getRow(T[] row, int[] widths, int lineLength, Printer<T> printer) {
final StringBuilder builder = new StringBuilder(lineLength).append(VERTICAL_BORDER);
final int maxWidths = widths.length;
for ( int i = 0; i < maxWidths; i++ ) {
builder.append(padRight(getCellValue(safeGet(row, i, printer), printer), widths[i])).append(VERTICAL_BORDER);
}
return builder.toString();
}
private static String getHorizontalBorder(int[] widths) {
final StringBuilder builder = new StringBuilder(256);
builder.append(BORDER_KNOT);
for ( final int w : widths ) {
for ( int i = 0; i < w; i++ ) {
builder.append(HORIZONTAL_BORDER);
}
builder.append(BORDER_KNOT);
}
return builder.toString();
}
private static int getMaxColumns(Object[][] rows) {
int max = 0;
for ( final Object[] row : rows ) {
if ( row != null && row.length > max ) {
max = row.length;
}
}
return max;
}
private static <T> void adjustColumnWidths(T[][] rows, int[] widths, Printer<T> printer) {
for ( final T[] row : rows ) {
if ( row != null ) {
for ( int c = 0; c < widths.length; c++ ) {
final String cv = getCellValue(safeGet(row, c, printer), printer);
final int l = cv.length();
if ( widths[c] < l ) {
widths[c] = l;
}
}
}
}
}
private static <T> String padRight(String s, int n) {
return format("%1$-" + n + "s", s);
}
private static <T> T safeGet(T[] array, int index, Printer<T> printer) {
return index < array.length ? array[index] : null;
}
private static <T> String getCellValue(T value, Printer<T> printer) {
return value == null ? DEFAULT_AS_NULL : printer.print(value);
}
}
和Printer.java：
public interface Printer<T> {
String print(T obj);
}
用法：
System.out.println(PrettyPrinter.print(some2dArray, new Printer<Integer>() {
@Override
public String print(Integer obj) {
return obj.toString();
}
}));
为什么要更改为T？好String是不够的，但我并不总是希望提供相同的输出obj.toString()，所以我使用界面可以随意更改。
第二个更改不是为类提供outstream，如果你想使用类似Logger的类（Log4j // Logback），你肯定会在使用流时遇到问题。
为什么更改只支持静态调用？我想把它用于记录器，只做一个电话就好了。