Arrays(java)

package com.arrays;
import java.util.Arrays;
public class Test { 
    public static void main(String[] args) { 
        int [] arr={ 11,22,44,88,66,33,55,77};
        //返回地址
        System.out.println(arr);  //[I@1b6d3586
        //返回数组的内容
        System.out.println(Arrays.toString(arr));  //[11, 22, 44, 88, 66, 33, 55, 77]
        //排序。升序
        Arrays.sort(arr);
        System.out.println(Arrays.toString(arr)); //[11, 22, 33, 44, 55, 66, 77, 88]
        //二分搜索技术，前提要排好序
        int i = Arrays.binarySearch(arr, 00);
        System.out.println(i);  //-1

        int i1 = Arrays.binarySearch(arr, 50);
        System.out.println(i1);  //-5 表示：-（应该插入的位置的索引+1）

    }
}

package com.arrays;

import java.util.Arrays;
import java.util.Comparator;

//comparator比较器对象
public class Test1 { 
    public static void main(String[] args) { 
        int [] arr={ 12,56,32,23,78,19};
        //Array的sort方法默认升序排序
        Arrays.sort(arr);
        System.out.println(Arrays.toString(arr));  //[12, 19, 23, 32, 56, 78]

        Integer [] arr1={ 12,56,32,23,78,19};
        Arrays.sort(arr1, new Comparator<Integer>() { 
            @Override
            public int compare(Integer o1, Integer o2) { 
                //指定规则
                /*if (o1>o2){ return 1; } else if (o1<o2){ return -1; } return 0;*/
                //return o1-o2; //默认升序 // //[12, 19, 23, 32, 56, 78]
                return o2-o1;   //降序 //[78, 56, 32, 23, 19, 12]
            }
        });
        System.out.println(Arrays.toString(arr1));
    }
}

package com.arrays;

public class Student { 
    String name;
    int age;
    double height;

    public Student() { 
    }

    public Student(String name, int age, double height) { 
        this.name = name;
        this.age = age;
        this.height = height;
    }

    public String getName() { 
        return name;
    }

    public void setName(String name) { 
        this.name = name;
    }

    public int getAge() { 
        return age;
    }

    public void setAge(int age) { 
        this.age = age;
    }

    public double getHeight() { 
        return height;
    }

    public void setHeight(double height) { 
        this.height = height;
    }

    @Override
    public String toString() { 
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", height=" + height +
                '}';
    }
}


package com.arrays;

import java.util.Arrays;
import java.util.Comparator;

public class StudentTest { 
    public static void main(String[] args) { 
        Student[] students=new Student[4];
        students[0]=new Student("小马哥",23,180.5);
        students[1]=new Student("小飞侠",32,183.5);
        students[2]=new Student("马奎斯",40,170.5);
        students[3]=new Student("罗西",20,190.5);

        Arrays.sort(students, new Comparator<Student>() { 
            @Override
            public int compare(Student o1, Student o2) { 
                //制定排序规则
                //按照年龄升序
                //return o1.getAge()-o2.getAge(); //[Student{name='罗西', age=20, height=190.5}, Student{name='小马哥', age=23, height=180.5}, Student{name='小飞侠', age=32, height=183.5}, Student{name='马奎斯', age=40, height=170.5}]
                //按照年龄降序
                //return o2.getAge()-o1.getAge(); //[Student{name='马奎斯', age=40, height=170.5}, Student{name='小飞侠', age=32, height=183.5}, Student{name='小马哥', age=23, height=180.5}, Student{name='罗西', age=20, height=190.5}]
                //按照身高升序排序
                //return Double.compare(o1.getHeight(),o2.getHeight()); //[Student{name='马奎斯', age=40, height=170.5}, Student{name='小马哥', age=23, height=180.5}, Student{name='小飞侠', age=32, height=183.5}, Student{name='罗西', age=20, height=190.5}]
                //按照身高降序
                return Double.compare(o2.getHeight(),o1.getHeight());  //[Student{name='罗西', age=20, height=190.5}, Student{name='小飞侠', age=32, height=183.5}, Student{name='小马哥', age=23, height=180.5}, Student{name='马奎斯', age=40, height=170.5}]
            }
        });
        System.out.print(Arrays.toString(students));

    }
}