Responsibility
• primary motivation is the need for a platform-independent (that is, architecture- neutral) language that could be used to create software to be embedded in various consumer electronic devices, such as microwave ovens and remote controls.
• Objects with clear responsibilities.
• Each class should have a clear responsibility.
• If you can't state the purpose of a class in a single, clear sentence, then perhaps your class structure needs some thought.
Messages
• We all like to use programs that let us know what's going on. Programs that keep us informed often do so by displaying status and error messages.
• These messages need to be translated so they can be understood by end users around the world.
• The Section discusses translatable text messages. Usually, you're done after you move a message String into a Resource Bundle.
• If you've embedded variable data in a message, you'll have to take some extra steps to prepare it for translation.
Methods
• A method is a group of instructions that is given a name and can be called up at any point in a program simply by quoting that name.
• Drawing a Triangle require draw of three straight lines. This instruction three times to draw a simple triangle.
• We can define a method to call this instruction three times and draw the triangle(i.e. create a method draw Line() to draw lines and this method is called repeatedly to achieve the needed task)
• The idea of methods appears in all programming languages, although sometimes it goes under the name functions and sometimes under the name procedures.
• The name methods is a throw-back to the language C++, from which Java was developed.
• In C++, there is an object called a class which can contain methods. However, everything in Java is enclosed within a class .so the functions within it are called methods