a2水 Objects and Messages (2) 4-16 An object that knows The data that how to print data should be printed System.out.println (area) Send the println message to this object Programming in Java JAVA
4-16 Programming in Java Objects and Messages (2) System.out.println (area) An object that knows how to print data Send the println message to this object The data that should be printed
域变量和局部变量 4. ·域变量 radius,area,和circumference都是域变量.它 们可以在类的任何地方被访问 ·局部变量 一在一个构造器或方法中声明，并只在该构造器 或方法中可用 -input是CircleCalcu1ator的局部变量 Programming in Java JAVA
4-17 Programming in Java 域变量和局部变量 • 域变量 – radius, area, 和 circumference 都是域变量. 它 们可以在类的任何地方被访问 • 局部变量 – 在一个构造器或方法中声明，并只在该构造器 或方法中可用 – input 是 CircleCalculator的局部变量
a2水 构造器声明 4-18 modifiers ClassName formalArgumentList local declarations and other statements } Programming in Java JAVA
4-18 Programming in Java 构造器声明 modifiers ClassName ( formalArgumentList ) { } local declarations and other statements