Java基础学习Day06

﹏ヽ暗。殇╰゛Y 2021-11-05 07:32 365阅读 0赞

#### 知识点 ####

1.  数组的动态初始化问题
2.  权限修饰符
3.  this
4.  构建类中方法快捷键

##### 数组的动态初始化问题 #####

public class Test {
        
    	public static void main(String[] args) {
        
    		int[] arr = new int[10];
    		System.out.println(arr.length);
    		System.out.println(arr[0]);
    	}
    }

结果是 10 0  
说明 动态初始化后 数组就分配好长度和初始值了

##### 权限修饰符 #####

<table> 
 <thead> 
  <tr> 
   <th align="center">修饰符</th> 
   <th align="center">同类</th> 
   <th align="center">同包</th> 
   <th align="center">外包子类</th> 
   <th align="center">外包</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">private</td> 
   <td align="center">√</td> 
   <td align="center">×</td> 
   <td align="center">×</td> 
   <td align="center">×</td> 
  </tr> 
  <tr> 
   <td align="center">default</td> 
   <td align="center">√</td> 
   <td align="center">√</td> 
   <td align="center">×</td> 
   <td align="center">×</td> 
  </tr> 
  <tr> 
   <td align="center">protect</td> 
   <td align="center">√</td> 
   <td align="center">√</td> 
   <td align="center">√</td> 
   <td align="center">×</td> 
  </tr> 
  <tr> 
   <td align="center">public</td> 
   <td align="center">√</td> 
   <td align="center">√</td> 
   <td align="center">√</td> 
   <td align="center">√</td> 
  </tr> 
 </tbody> 
</table>

##### this #####

this可以调用本类中的方法和属性以及构造方法  
调用无参构造方法时 this.类名()  
调用带参构造方法时 this.类名(参数列表)

##### 构建类中方法快捷键 #####

Alt + Shift + S

#### 课后作业 ####

1.  使用get set方法实例化3个学生

package com.day06;
    
    public class Student {
        
    	private String name;
    	private int age;
    	private char sex;
    	
    	public String getName() {
        
    		return name;
    	}
    	public void setName(String name) {
        
    		this.name = name;
    	}
    	public int getAge() {
        
    		return age;
    	}
    	public void setAge(int age) {
        
    		this.age = age;
    	}
    	public char getSex() {
        
    		return sex;
    	}
    	public void setSex(char sex) {
        
    		this.sex = sex;
    	}
    }

package com.day06;
    
    public class Test {
        
    	public static void main(String[] args) {
        
    		Student s1 = new Student();
    		Student s2 = new Student();
    		Student s3 = new Student();
    		
    		s1.setName("小明");
    		s1.setAge(11);
    		s1.setSex('男');
    		
    		s2.setName("小红");
    		s2.setAge(10);
    		s2.setSex('女');
    		
    		s3.setName("小华");
    		s3.setAge(13);
    		s3.setSex('男');
    		
    		System.out.println(s1.getName() + "\t" + s1.getSex() + "\t" + s1.getAge());
    		System.out.println(s2.getName() + "\t" + s2.getSex() + "\t" + s2.getAge());
    		System.out.println(s3.getName() + "\t" + s3.getSex() + "\t" + s3.getAge());
    	}
    }