Object类-try-catch-finally-throw-throws-自定义异常

  1 //覆写toString()
  2  class Person{
  3      private String name;
  4      private int age;
  5 
  6     public Person(String name, int age){
  7          this.name = name;
  8          this.age = age;
  9      }
 10 
 11     public String getName(){
 12          return this.name;
 13      }
 14 
 15     public int getAge(){
 16          return this.age;
 17      }
 18 
 19     @Override
 20      public String toString(){
 21         StringBuilder sb = new StringBuilder();
 22          sb.append("name:").append(this.name).append("\t").append("age:").append(this.age);
 23          return sb.toString();
 24      }
 25 
 26     @Override
 27      public boolean equals(Object obj){
 28          //首先判断地址值,地址值相等则一定是同一对象
 29         if(this == obj){
 30              return true;
 31          }
 32 
 33         //然后判断是否是同一类,若不是同一类,则必定不相等
 34         if(!(obj instanceof Person)){
 35              return false;
 36          }
 37 
 38         //如果是同一类,则比较其属性,属性相同,则为同一事物
 39         Person p = (Person) obj;
 40          if(this.name == p.name && this.age == p.age){
 41              return true;
 42          }else{
 43              return false;
 44          }
 45 
 46      }
 47  }
 48 
 49 
 50  public class PersonDemo{
 51      public static void main(String[] args){
 52          Person p = new Person("zhangsan",20);
 53          Person p1 = new Person("zhangsan",20);
 54          Person p2 = new Person("zhangsan1",20);
 55          System.out.println(p);
 56          System.out.println(p.equals(p1));
 57          System.out.println(p.equals(p2));
 58      }
 59  }
 60 

  1 class ArrayTools{
  2      public static int getElement(int[] arr, int index){
  3 
  4          if(arr == null){
  5              throw new NullPointerException("arr指向的数组不存在");
  6          }
  7 
  8         if(index < 0 || index >= arr.length){
  9              throw new ArrayIndexOutOfBoundsException("错误的角标"+index+"索引在数组中不存在");
 10          }
 11 
 12         int element = arr[index];
 13 
 14         return element;
 15      }
 16  }
 17 
 18 public class ExceptionDemo{
 19      public static void main(String[] args){
 20          int[] arr = {1,2,3};
 21          //int num = ArrayTools.getElement(null,2);//ExceptionDemo.java:21
 22          int num1 = ArrayTools.getElement(arr,5);//ExceptionDemo.java:22
 23          //System.out.println("num="+num);
 24          System.out.println("num1="+num1);
 25      }
 26  }
 27 

  1 //import java.io.*;
  2  import java.io.FileReader;
  3  import java.io.FileNotFoundException;
  4  import java.io.IOException;
  5 
  6 public class ExceptionTest{
  7      public static void main(String[] args) throws FileNotFoundException,IOException{
  8          FileReader fr = new FileReader("a.txt");//ExceptionTest.java:8
  9          int c = fr.read();
 10          System.out.println(c);
 11      }
 12  }
 13 

  1 import java.io.IOException;
  2  import java.io.FileReader;
  3 
  4 public class TryTest{
  5      public static void main(String[] args){
  6          FileReader fr = null;
  7          try{
  8          int c = fr.read();  //TryTest.java:8
  9          System.out.println(c);
 10          }catch(IOException e){
 11              System.out.println("读取文件时出现了异常");
 12          }finally{
 13              if(fr != null){
 14                  try{
 15                      fr.close();
 16                  }catch(IOException e){
 17                      System.out.println("关闭流时出现了问题");
 18                  }
 19              }
 20          }
 21 
 22     }
 23  }
 24 

  1 class NoAgeException extends Exception{
  2      NoAgeException(){
  3          super();
  4      }
  5 
  6     NoAgeException(String message){
  7          super();
  8      }
  9  }
 10 
 11 class Person{
 12      private String name;
 13      private int age;
 14 
 15     Person(String  name, int age) throws NoAgeException{
 16          if(age <  0 || age > 200){
 17              throw new NoAgeException("年龄数值非法");
 18          }
 19 
 20         this.name = name;
 21          this.age = age;
 22      }
 23 
 24     public String toString(){
 25          return "name="+name+"age="+age;
 26      }
 27  }
 28 
 29 public class ExceptionDemoTest{
 30      public static void main(String[] args){
 31          try{
 32              Person p  = new Person("xiaoming", 20);
 33              System.out.println(p);
 34          }catch(NoAgeException ex){
 35             System.out.println("年龄异常");
 36          }
 37          System.out.println("over");
 38      }
 39  }
 40