修改后的 Counter 类如下
class Counter {
private var value = 0
def increment() {
if ( value == Int.MaxValue ) {
value = 0
} else {
value += 1
}
}
def current() = value
}
BankAccount 类如下
class BankAccount( private var _balance: Double ) {
def balance = _balance
def deposit( d: Double ) {
_balance += d
}
def withdraw( d: Double ): Double = {
val rd = d.min( _balance )
_balance -= rd
rd
}
}
类实现如下
class Time( val hours: Int, val minutes: Int ) {
def before( other: Time ): Boolean = {
( hours < other.hours ) ||
(( hours == other.hours ) && ( minutes < other.minutes ))
}
}
修改后的类如下
class Time( val hours: Int, val minutes: Int ) {
def this( minutes: Int ) {
this( minutes / 60, minutes % 60 )
}
def before( other: Time ): Boolean = {
( hours < other.hours ) ||
(( hours == other.hours ) && ( minutes < other.minutes ))
}
}
代码如下，其中 name 为 JavaBeans 属性，id 为正常 scala 属性
import scala.reflect.BeanProperty
class Student {
@BeanProperty var name: String = "";
var id: Long = 0
}
生成的 Student 类中生成的方法有
private java.lang.String name;
private long id;
public java.lang.String name();
public void name_$eq(java.lang.String);
public void setName( java.lang.String );
public long id();
public void id_$eq(long0;
public java.lang.String getName();
public Student();
scala 中调用 JavaBeans 方法如下
val s = new Student
s.setName( "larry" )
println( s.getName )
类代码如下
class Person( _age: Int ) {
var age = _age.max(0)
}
类代码如下
class Person( name: String ) {
val firstName = name.split( " " )(0)
val lastName = name.split( " " )(1)
}
主构造器参数是普通参数，因为没有对该参数的访问需要
主构造器使用
class Car( val manufacturer: String, val genere: String,
val year: Int = -1,
var plate: String = "" ) {
}
使用默认参数可以避免过多的辅助构造器
如果用 Java 来实现上面的类，代码如下（比 scala 复杂的多）
public class Car {
private String manufacturer;
private String genere;
private int year;
public String plate;
public int year() {
return year;
}
public String genere() {
return genere;
}
public String manufacturer() {
return manufacturer;
}
public Car( String m, String g, int y, String p ) {
this.manufacturer = m;
this.genere = g;
this.year = y;
this.plate = p;
}
public Car( String manufacturer, String genere, int year ) {
this( manufacturer, genere, year, "" );
}
public Car( String manufacturer, String genere, String plate ) {
this( manufacturer, genere, -1, plate );
}
public Car( String manufacturer, String genere ) [
this( manufacturer, genere, -1 );
}
}
使用缺省参数，代码更少，同时更强调了默认的参数。代码如下
class Employee( val name: String = "John Q. Public",
var salary: Double = 0.0 ) {
}