Members of the two classes: Method

The conceptual approach

Method (method), also known function (function), is an independent representative of reusable functions, reflecting the affairs of behavioral characteristics, functional characteristics.

Purpose / Benefits: Reusability

The method of grammar

1, method statement format:

[Modifier] The method return type name (parameter list []) { 
    Method member 
}

Description:

(1) [modifiers]

(2) Return Value Type: Java can be any type of data, including basic data types and the reference data type.

When the method does not return a value, expressed using the void.

  • If the return value type of the method is void, then the method body in {} return statement may not be required.

  • If the method is not a void return type, there must return a return value in {} in the method body; statements, or the compiler is not passed.

(3) the method name:

  • Try to represent the method of function, that is intended to see to know the name of

  • From the beginning of the second word capitalized

(4) [parameter list]: said in completion of the current method, we need to "caller" Give me the extra data.

  • A list format parameter: (a data type parameter name, the data type parameter name ....)

  • The method requires the number of the "caller" when calling the method, the argument list [], the type, the sequence must correspond] [parameter list.

(5) Procedure: implement the functions of the method, preferably a method to complete a separate function.

2, call the format method:

// This method calls similar level 
directly using 

class Circle { 
    Double RADIUS; 
    
    Double Area () { 
        return * 3.14 * RADIUS RAIDUS; 
    } 
    
    String getInfo () { 
        return "Radius:" + radius + ", Area:" + area ( ); 
    } 
} 
// call from another class of 
the object name method name ([argument list]). 

class Circle { 
    Double RADIUS; 
    
    Double Area () { 
        return * 3.14 * RADIUS RAIDUS; 
    } 
} 
class TestCircle { 
    public static main void (String [] args) { 
        Circle Circle new new C = (); 
        System.out.println ( "radius:" + c.raidus + ", area:" + c.area ()); 
    } 
}

  

(1) whether the mass participation

  • Methods [see whether the argument list parameter list] [], the number, type, and order parameter list] [correspondence;

  • Whether or not there are parameters, do not omit the call ()

(2) whether to receive the return value

  • To see whether the method has a return value, if the void is, that there is no return value, can not be received;

  • If it is not void, it can receive, and receiving the return value of a variable of type must be compatible with the type of the return value.

Sample code and declaration called 3, the method of

(1) None None Return Value Method Reference

// This class 
class Demo { 
    void test1 () { 
        // .... 
    } 
    
    void test2 () { 
        test1 (); // directly 
    } 
} 

// Other types of 
class Demo1 { 
    void test1 () { 
        // .. .. 
    } 
} 
class Demo2 { 
    void test2 () { 
        Demo1 Demo1 new new D = (); 
        d.test1 (); 
    } 
}

  (2) method returns a value has no parameters

// This class 
class Circle { 
    Double RADIUS; 
    
    Double Area () { 
        return * 3.14 * RADIUS RAIDUS; 
    } 
    / * 
    String getInfo () { 
        return "Radius:" + radius + ", Area:" + area (); // directly connected together, the return value area () method. 
    *} / 
    String getInfo () { 
        Double a = Area (); // return the received value a variable 
        return "Radius:" + radius + ", Area:" + a; 
    } 
} 

// Other types of 
class Circle { 
    Double RADIUS; 
    
    Double Area () { 
        return * 3.14 * RADIUS RAIDUS; 
    } 
} 
class TestCircle { 
    public static void main (String [] args) { 
        Circle Circle new new C = ();
        System.out.println ( "Radius:" + c.raidus + ", Area:" + c.area ()); 
        
        Double c.area a = (); // with a variable receives the return value 
        System.out.println ( "radius:" + c.raidus + ", area:" + A); 
    } 
}

  3) None Return Value Method Reference

//本类
class Demo{
    void test1(String str){
        //....
    }
    
    void test2(){
        test1("hello");
    }
}

//其他类
class Demo1{
    void test1(String str){
        //....
    }   
    
}
class Demo2{
    void test2(){
        Demo1 d = new Demo1();
        d.test1("hello");
    }
}

  (4) method returns a value with a reference

//本类
class Demo{
    int max(int a, int b){
        return a>b?a:b;
    }
    
    void test(){
        int m = max(3,4);
        System.out.println("最大值:" +m);
    }
}

//其他类
class Demo1{
    int max(int a, int b){
        return a>b?a:b;
    }
}
class Demo2{
    void test2(){
        Demo1 d = new Demo1();
        int m = d.max(4,5);
        System.out.println("最大值:" +m);
    }
}

  

4, the principle of the method declaration and call

(1) method must be declared after the call

If you call the method, if the method name wrong or calling a method that does not exist, the compiler will complain

Position (2) The method must be declared in the class outer Method

Right:

Class { 
    1 () { 
        
    } 
    Method 2 () { 
        
    } 
}

Examples of errors:

Class { 
    1 () { 
        Method 2 () {// error 
        
   		} 
    } 
}

  

Where the call (3) required by the method

Right:

Class { 
    1 () { 
        calling method 
    } 
}

  Examples of errors:

Class { 
    1 () { 
        
    } 
    
    calling methods // position error 
}

Call format (4) of the method to correspond with the declaration format method

① whether to add "objects."

② Do you want to receive the return value

③ Do you want to pass parameters

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Origin www.cnblogs.com/panyizuoshan/p/11448517.html