Java语言

王晓蒙

目录

  • 1 Introduction to Java
    • 1.1 Programming Languages
    • 1.2 Java Introduction
    • 1.3 JDK Installation
    • 1.4 A Simple Program
    • 1.5 Programming Style and Documentation
    • 1.6 Programming Error
    • 1.7 Programming Using Eclipse
    • 1.8 Review Questions
  • 2 Elementary Programming
    • 2.1 Identifiers, Variables and Constants
    • 2.2 Input By Console
    • 2.3 Numeric Data Type and Literals
    • 2.4 Augmented Numeric Operators
    • 2.5 Numeric Type Conversions
    • 2.6 Mathematical Methods
    • 2.7 Character Data Type
    • 2.8 Using String Type
    • 2.9 Console Formatting Output
  • 3 Selections
    • 3.1 Boolean and Relational Operators
    • 3.2 if-else
    • 3.3 Logical Operators
    • 3.4 switch
  • 4 Loops
    • 4.1 while
    • 4.2 Case: Guessing Numbers
    • 4.3 do-while
    • 4.4 for
    • 4.5 Nested Loops
    • 4.6 break and continue
    • 4.7 Case: Checking Palindromes
  • 5 Methods
    • 5.1 Defining and Calling a Method
    • 5.2 Passing Arguments By Values
    • 5.3 Modularizing Code
    • 5.4 Overloading Methods
    • 5.5 Variables Scope
  • 6 Arrays
    • 6.1 Array Basics
    • 6.2 Case: Analyzing Numbers
    • 6.3 Copying Arrays
    • 6.4 Passing Arrays to Methods
    • 6.5 Variable-Length Arguments List
    • 6.6 The Arrays Class
    • 6.7 Two-Dimensional Arrays Basics
    • 6.8 Two-Dimensional Arrays Processing
    • 6.9 Multidimensional Arrays
  • 7 Objects and Classes
    • 7.1 Introduction to OOP
    • 7.2 Defining Classes and Creating Objects
    • 7.3 Constructors
    • 7.4 Reference Variables and Reference Types
    • 7.5 Using Java Library
    • 7.6 Static Members
    • 7.7 Visibility Modifers
    • 7.8 Passing Objects to Methods
    • 7.9 This Keyword
    • 7.10 Wrapper Class
    • 7.11 Immutable and Interned Strings
  • 8 Inheritance and Polymorphism
    • 8.1 Super-classes and Sub-classes
    • 8.2 super Keyword and Constructor Chaining
    • 8.3 Overriding
    • 8.4 Polymorphism
    • 8.5 Objects Casting
    • 8.6 The method equals
    • 8.7 The protected Members
  • 9 Abstract Classes and Interfaces
    • 9.1 Abstract Classes
    • 9.2 Interfaces
    • 9.3 Comparable Interface
  • 10 Exception Handling
    • 10.1 Introduction
    • 10.2 Exception Declaring and Throwing
    • 10.3 Exception Catching and Handling
    • 10.4 finally
  • 11 I/O Operation
    • 11.1 I/O Introduction
    • 11.2 Binary Input
    • 11.3 Binary Output
    • 11.4 Text Input
    • 11.5 Text Output
  • 12 JavaFX Basics
    • 12.1 A Basic JavaFX Program
    • 12.2 Node Types
    • 12.3 Property Binding
    • 12.4 Node Style
    • 12.5 Layout
    • 12.6 JavaFX and Eclipse
  • 13 Event-Driven Programming
    • 13.1 Event-Source, Event and Event-Handler
    • 13.2 Defining Event-Handler Using Inner-Class
    • 13.3 Event Handling Using Lambda Expression
  • 14 Others
Introduction



Exception handling

Exception handling enables a program to deal with exceptional situations and continue its normal execution. In Java, runtime errors are thrown as exceptions. An exception is an object that represents an error or a condition that prevents execution from proceeding normally. If the exception is not handled, the program will terminate abnormally. How can you handle the exception so that the program can continue to run or else terminate gracefully?（在Java中，异常处理是指将程序运行中发生的异常或错误作为对象抛出并进行处理的过程，异常处理使得程序在发生异常后能继续执行或“温和”地终止）


Case Study

Inputting method without exception handling.









当输入不合法时，程序发生异常终止







Inputting method with exception handling.













input.nextInt()函数执行时，可能会抛出InputMismatchException类型的异常。为避免输入不合法时程序异常终止，这里需要用try-catch语句对该类异常进行捕获和处理，处理方式有两种：一是捕获到异常后打印提示信息，让程序自然终止；二是捕获异常后让用户重新输入，直到输入正确。这里借助do-while循环采用了第二种异常处理方式，其运行效果如下