我知道这个问题可能已经被问过了，但我找不到一个合适的答案。假设我有这个数组：
String[][] theArray = {
{"james", "30.0"},
{"joyce", "35.0"},
{"frank", "3.0"},
{"zach", "34.0"}};
theArray = {
{"joyce", "35.0"},
{"zach", "34.0"},
{"james", "30.0"},
{"frank", "3.0"}};
Arrays.sort(arr, comparator)：Arrays.sort(theArray, new Comparator<String[]>(){
@Override
public int compare(final String[] first, final String[] second){
// here you should usually check that first and second
// a) are not null and b) have at least two items
// updated after comments: comparing Double, not Strings
// makes more sense, thanks Bart Kiers
return Double.valueOf(second[1]).compareTo(
Double.valueOf(first[1])
);
}
});
System.out.println(Arrays.deepToString(theArray));
输出：
[[joyce，35.0]，[zach，34.0]，[james，30.0]，[frank，23.0]]
注意：
你将对传入的数组进行排序，Arrays.sort() 不会返回一个新的数组（实际上它返回 void）。如果你想要一个排序后的副本，请这样做：
String[][] theCopy = Arrays.copyOf(theArray, theArray.length);
排序应该在theCopy上进行，而不是在theArray上进行。
public class StrinArrayComparator implements Comparator<String[]> {
@Override
public int compare(String[] array1, String[] array2) {
// get the second element of each array, andtransform it into a Double
Double d1 = Double.valueOf(array1.[1]);
Double d2 = Double.valueOf(array2.[1]);
// since you want a descending order, you need to negate the
// comparison of the double
return -d1.compareTo(d2);
// or : return d2.compareTo(d1);
}
}
如果你想摆脱数组，这里有一种使用 List<Record> 和一个实现了 Comparator<Record> 接口的 RecordComparator 的变体。
控制台：
joyce 35.0 zach 34.0 james 30.0 frank 23.0
代码：
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/** @see https://dev59.com/P1TTa4cB1Zd3GeqPtIVp */
public class ComparatorTest {
public static void main(String[] args) {
List<Record> list = new ArrayList<Record>(Arrays.asList(
new Record("james", "30.0"),
new Record("joyce", "35.0"),
new Record("frank", "23.0"),
new Record("zach", "34.0")));
print(list, Sort.DESCENDING, Field.D);
}
private static void print(List<Record> list, Sort s, Field f) {
RecordComparator rc = new RecordComparator(s, f);
Collections.sort(list, rc);
for (Record r : list) {
System.out.println(r);
}
}
}
class Record {
private String s;
private Double d;
public Record(String name, String number) {
this.s = name;
this.d = Double.valueOf(number);
}
@Override
public String toString() {
return s + " " + d;
}
public int compareTo(Field field, Record record) {
switch (field) {
case S: return this.s.compareTo(record.s);
case D: return this.d.compareTo(record.d);
default: throw new IllegalArgumentException(
"Unable to sort Records by " + field.getType());
}
}
}
enum Sort { ASCENDING, DESCENDING; }
enum Field {
S(String.class), D(Double.class);
private Class type;
Field(Class<? extends Comparable> type) {
this.type = type;
}
public Class getType() {
return type;
}
}
class RecordComparator implements Comparator<Record> {
private Field field;
private Sort sort;
public RecordComparator(Sort sort, Field field) {
this.sort = sort;
this.field = field;
}
@Override
public final int compare(Record a, Record b) {
int result = a.compareTo(field, b);
if (sort == Sort.ASCENDING) return result;
else return -result;
}
}
public class Person {
private final String name;
private final double score;
public Person(final String name, final double score) {
this.name=name;
this.score=score;
}
public String getName() {
return name;
}
public double getScore() {
return score;
}
}
Comparator<Person>指定您想要它们排序的方式：public PersonScoreComparator implements Comparator<Person> {
public int compare(Person p1, Person p2) {
return Double.compare(p1.getScore(), p2.getScore());
}
}
Comparable<Person>：public int compareTo(Person other) {
return Double.compare(getScore(), other.getScore());
}
公共静态无返回值主函数(String[] args) {
String Name[][]={{"prakash","kumar"},{"raj","kappor"},{"vinod","bhart"}};
String str[]=new String[2];
for(int j=0; j<Name.length;j++)
{
for (int i=0 ; i<2; i++)
{
str[i]=Name[j][i];
}
for(int i=0;i<str.length;i++)
{
for(int k=i+1;k<str.length;k++)
{
if(str[i].compareTo(str[k])>0)
{
String temp= str[i];
str[i]=str[k];
str[k]=temp;
}
}
System.out.print(str[i]+ " ");
}
System.out.println();
}
}
}
Arrays.asList()，而不是 Arrays.toList()，并且你不需要它，因为还有 Arrays.sort()。 - Sean Patrick Floydjava.util.Arrays中有几种排序方法。其中两种采用自定义的Comparator。只需提供一个比较内部数组第二个元素的比较器即可。
/**
*
* @param array - 2D array required to be arranged by certain column
* @param columnIndex - starts from 0; this will be the main comparator
* @param hasHeaders - true/false; true - ignore the first row. False -
* first row it's also compared and arranged
* @return - the new arranged array
*/
private String[][] arrangeArray(String[][] array, int columnIndex, boolean hasHeaders) {
int headersExists = 0;
if (hasHeaders) {
headersExists = 1;
}
for (int i = headersExists; i < array.length; i++) {
for (int j = headersExists; j < array.length; j++) {
if (array[i][columnIndex].compareTo(array[j][columnIndex]) < 0){
String[] temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}
return array;
}