java小基础之方法与构造方法
书写方式
1.方法定义格式
返回值类型 方法名称(参数列表)
{
代码..
}
2.构造方法
Person p =
new Person(
"张三",
20,
123.0);
3.注意事项
(
1)如果你没写无参的构造方法系统会给你提供一个无参的构造方法
(
2)如果我只写了有参的构造方法
这时系统就不会给你提供无参的构造方法
(
3)写类的时候 建议 无参有参构造方法全写
代码解析
public class Object {
public static void main(String[] args) {
Person p =
new Person();
p.name =
"张扇";
p.age =
20;
p.introduce();
p.abs(-
10);
System.
out.println(
"-10的绝对值是"+p.abs(-
10));
}
}
class Person
{
String name ;
int age;
double height;
void introduce() {
System.
out.println(
"大家好,我叫" + name +
"我今年" + age +
"岁");
}
Person() {}
Person(String n,
int a,
double h) {
this(
"张三",
5);
name = n;
age = a;
height = h;
}
Person(String n,
int a) {
name = n;
age = a;
}
int abs(
int a){
int r;
if(a >=
0)
{
r = a;
}
else {
r =-a;
}
return r;
}
double abs(
double a){
double r;
if(a >=
0)
{
r = a;
}
else {
r =-a;
}
return r;
}
public class Object01 {
public static void main(String[] args) {
Person p =
new Person(
"张三",
20,
123.0);
Person p1 =
new Person(
"李四",
50,
56.59);
Person p2 =
new Person(
"王五",
50);
System.
out.println(
"p.name " + p.name);
System.
out.println(
"p.age " + p.age);
System.
out.println(
"p1.name " + p1.name);
System.
out.println(
"p1.age " + p1.age);
System.
out.println(
"p2.name " + p2.name);
System.
out.println(
"p2.age " + p2.age);
}
}