我正在嘗試編寫(xiě)一個(gè)比較器來(lái)比較 Coordinate 類(lèi)的兩個(gè)對(duì)象。Coordinate 類(lèi)非常簡(jiǎn)單：public class Coordinate { private int x, y; public Coordinate(int x, int y) { this.x = x; this.y = y; } public int getX() { return x; } public void setX(int x) { this.x = x; } public int getY() { return y; } public void setY(int y) { this.y = y; }}現(xiàn)在我想讓 Comparator 比較 Coordinate 類(lèi)的兩個(gè)實(shí)例的 x 和 y 值。這是一個(gè)例子：我有一個(gè)坐標(biāo) c1，它有 x = 42 和 y = 23。我的第二個(gè)坐標(biāo) c2 有 x = 23 和 y = 54。現(xiàn)在我把它們都放在一個(gè) ArrayList 中，想要對(duì)列表進(jìn)行排序。我想按以下方式排序：具有最低 y 值的坐標(biāo)始終排在第一位，當(dāng)您有兩個(gè)具有相同 y 值的坐標(biāo)時(shí)，該坐標(biāo)排在第一位，其 x 值較低。例子：c1 (y = 4, x = 5 ) < c2 (y = 4, x = 6) < c3 (y = 5, x = 2) 那么我怎樣才能為此目的編寫(xiě)一個(gè)比較器呢？
2 回答
慕的地8271018
TA貢獻(xiàn)1796條經(jīng)驗(yàn) 獲得超4個(gè)贊
Comparator<Coordinate> c = Comparator.comparingInt(Coordinate::getY)
.thenComparingInt(Coordinate::getX);
您可以通過(guò)thenComparing和構(gòu)建復(fù)合比較器thenComparingX。
var list = List.of(
new Coordinate(6, 4),
new Coordinate(2, 5),
new Coordinate(5, 4)
);
list.sort(c);
System.out.println(list);
片段打印
[{y=4, x=5}, {y=4, x=6}, {y=5, x=2}]
30秒到達(dá)戰(zhàn)場(chǎng)
TA貢獻(xiàn)1828條經(jīng)驗(yàn) 獲得超6個(gè)贊
使用比較器
import java.util.ArrayList;
import java.util.Comparator;
class Coordinate {
private int x, y;
public Coordinate(int x, int y) {
this.x = x;
this.y = y;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public String toString() {
return "x = " + x + " y = " + y;
}
}
public class Temp {
public static void main(String[] args) {
ArrayList<Coordinate> A = new ArrayList<>();
A.add(new Coordinate(1, 2));
A.add(new Coordinate(2, 1));
A.add(new Coordinate(3, 2));
A.sort(new Comparator<Coordinate>() {
@Override
public int compare(Coordinate o1, Coordinate o2) {
if (o1.getY() < o2.getY()) {
return -1;
} else if (o1.getY() > o2.getY()) {
return 1;
} else {
if (o1.getX() < o2.getX()) {
return -1;
} else if (o1.getX() > o2.getX()) {
return 1;
}
return 0;
}
}
});
System.out.println(A.toString());
}
}
使用可比較的接口
import java.util.ArrayList;
class Coordinate implements Comparable<Coordinate> { # Notice implementing Comparable interface
private int x, y;
public Coordinate(int x, int y) {
this.x = x;
this.y = y;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
@Override
public int compareTo(Coordinate o) { # implementing the abstract method of Comparable interface
if (y < o.y) {
return -1;
} else if (y > o.y) {
return 1;
} else {
if (x < o.x) {
return -1;
} else if (x > o.x) {
return 1;
}
return 0;
}
}
public String toString() {
return "x = " + x + " y = " + y;
}
}
public class Temp {
public static void main(String[] args) {
ArrayList<Coordinate> A = new ArrayList<>();
A.add(new Coordinate(1, 2));
A.add(new Coordinate(2, 1));
A.add(new Coordinate(3, 2));
A.sort(null);
System.out.println(A.toString());
}
}
輸出
[x = 2 y = 1, x = 1 y = 2, x = 3 y = 2]
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