1.统计学生对象数组中男女生人数以及平均年龄

class StudentsTest {
    String studentname;//null
    char studentgender;//'\u0000'
    int studentage;//0

    public StudentsTest(String studentname, char studentgender, int studentage) {
        this.studentname = studentname;
        this.studentgender = studentgender;
        this.studentage = studentage;
    }
    public StudentsTest() {}
}
public class StudentsArrayTest{
    static int averageAge;
    public static void main(String[] args){
        StudentsTest [] studentsTests={
                new StudentsTest("huang",'a',10),
                new StudentsTest(),
                new StudentsTest("wang",'男',11),
                new StudentsTest("jing",'男',12),
                new StudentsTest("li",'男',13),
                new StudentsTest("sun",'女',14),
                new StudentsTest(null,'女',15),
                new StudentsTest("Li",'b',16),
                new StudentsTest("gao",'女',17),
                new StudentsTest("zhao",'女',18)
        };
        statistics(studentsTests);
    }
    public static void statistics(StudentsTest[] students){
        int numberOfMale=0;
        int numberOfFemale=0;
        int age=0;
        for (StudentsTest student:students){
            age+=student.studentage;
            if ('男'==student.studentgender){
                numberOfMale++;
            }else if ('女'==student.studentgender){
                numberOfFemale++;
            }else {;}
        }
        averageAge=age/students.length;
        System.out.println(numberOfMale+"男"+numberOfFemale+"女");
        System.out.println("平均年龄："+averageAge);
    }
}

2.static用法-修饰方法举例

class Waterglass {
    String owner;
    String content;

    public Waterglass() {}
    public Waterglass(String owner, String content) {
        this.owner = owner;
        this.content = content;
    }

    public static void change(Waterglass waterglass){
        waterglass=new Waterglass("张无忌","可口可乐");
        show(waterglass);
    }


    public static void show(Waterglass waterglass){
        System.out.println(waterglass.owner+"的杯里装着"+waterglass.content);
    }

}
public class WaterglassTest{
    public static void main(String[] args){
        Waterglass waterglass1=new Waterglass("张三丰","白开水(烧的不错)");
        Waterglass.show(waterglass1);
        Waterglass.change(waterglass1);
        Waterglass.show(waterglass1);
    }
}