public static void sayHi(){
System.out.println("Hi!");
}
public static void main(String[] args){
sayHi();
}
public static void sayHi(String name){
System.out.println("Hi!" + name);
}
public static void main(String[] args){
sayHi("Tom");
sayHi("Bob");
}
[vagrant@localhost java]$ javac MyApp.java
[vagrant@localhost java]$ java MyApp
Hi!Tom
Hi!Bob
public static String sayHi(String name){
return "Hi!" + name;
}
public static void main(String[] args){
String msg = sayHi("Steve");
System.out.println(msg);
}
[vagrant@localhost java]$ javac MyApp.java
[vagrant@localhost java]$ java MyApp
Hi!Steve
classを使ってみよう
class User {
String name = "Me!";
void sayHi(){
System.out.println("hi!");
}
}
public class MyApp {
public static void main(String[] args){
User tom;
tom = new User();
System.out.println(tom.name);
tom.sayHi();
}
}
[vagrant@localhost java]$ javac MyApp.java
[vagrant@localhost java]$ java MyApp
Me!
hi!
なるほど。
コンストラクタ
class User {
String name;
User(String name){
this.name = name;
}
void sayHi(){
System.out.println("hi!" + this.name);
}
}
public class MyApp {
public static void main(String[] args){
User tom;
tom = new User("Tom");
System.out.println(tom.name);
tom.sayHi();
}
}
[vagrant@localhost java]$ javac MyApp.java
[vagrant@localhost java]$ java MyApp
Tom
hi!Tom
なるほど、何故か急に分かってきた。
classの継承
class User {
String name;
User(String name){
this.name = name;
}
void sayHi(){
System.out.println("hi!" + this.name);
}
}
class AdminUser extends User {
AdminUser(String name){
super(name);
}
void sayHello(){
System.out.println("hello!" + this.name);
}
}
public class MyApp {
public static void main(String[] args){
User tom = new User("Tom");
System.out.println(tom.name);
tom.sayHi();
AdminUser bob = new AdminUser("bob");
System.out.println(bob.name);
bob.sayHi();
bob.sayHello();
}
}
@override 継承した時に親クラスのメソッドを使う
class User {
String name;
User(String name){
this.name = name;
}
void sayHi(){
System.out.println("hi!" + this.name);
}
}
class AdminUser extends User {
AdminUser(String name){
super(name);
}
void sayHello(){
System.out.println("hello!" + this.name);
}
@Override void sayHi(){
System.out.println("[admin]hi!" + this.name);
}
}
public class MyApp {
public static void main(String[] args){
User tom = new User("Tom");
System.out.println(tom.name);
tom.sayHi();
AdminUser bob = new AdminUser("bob");
System.out.println(bob.name);
bob.sayHi();
bob.sayHello();
}
}
[vagrant@localhost java]$ javac MyApp.java
[vagrant@localhost java]$ java MyApp
Tom
hi!Tom
bob
[admin]hi!bob
hello!bob
ほうほう
