方法一
public static <T> int binarySearch(List<? extends Comparable<? super T>> list, T key)
此方法傳入一個實現了Comparable接口的對象類的列表和要查找的元素。
創建實現了Comparable接口的對象類
public class Student1 implements Comparable<Student1> {
private String name;
private int age;
public Student1() {
}
public Student1(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public int compareTo(Student1 s) {
int num = this.age - s.age;
int num1 = (num == 0 ? this.name.compareTo(s.name) : num);
return num1;
}
}
調用
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import cn.stone.comparable_comparator.Student1;
public class Student1Test {
public static void main(String[] args) {
List<Student1> list1 = new ArrayList<Student1>();
list1.add(new Student1("林青霞", 27));
list1.add(new Student1("風清揚", 30));
list1.add(new Student1("劉曉曲", 28));
list1.add(new Student1("武鑫", 29));
list1.add(new Student1("林青霞", 27));
int index=Collections.binarySearch(list1, new Student1("林青霞", 27));
System.out.println(index);
}
}
方法二
public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c)
此方法傳入一個列表，要查找的元素，以及一個比較器。
創建對象類
public class Student2 {
private String name;
private int age;
public Student2() {
}
public Student2(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}
調用
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import cn.stone.comparable_comparator.Student2;
public class Student2Test {
public static void main(String[] args) {
List<Student2> list2 = new ArrayList<Student2>();
list2.add(new Student2("林青霞", 27));
list2.add(new Student2("風清揚", 30));
list2.add(new Student2("劉曉曲", 28));
list2.add(new Student2("武鑫", 29));
list2.add(new Student2("林青霞", 27));
int index1 = Collections.binarySearch(list2, new Student2("林青霞", 27),
new MyComparator());
System.out.println(index1);
}
}
class MyComparator implements Comparator<Student2> {
@Override
public int compare(Student2 s1, Student2 s2) {
int num = s1.getAge() - s2.getAge();
int num1 = (num == 0 ? s1.getName().compareTo(s2.getName()) : num);
return num1;
}
}