UML Basic introduction

UML chart

1. Use case diagram
2. Static structure diagram ： Class diagram 、 Object graph 、 Package diagram 、 Component diagram 、 Deployment diagram
3. Dynamic behavior diagram ： Interaction diagram ( Sequence diagrams and collaboration diagrams )、 State diagram 、 Activity diagrams

Relationship between classes

Dependency relationship

As long as it's in the Class needs to use each other , Then there is a dependency between them , If there is no class used , Unable to compile

1. Member variables of class
2. The return type of the method in the class
3. Type of parameter received by method in class
4. Method used in

class B{
    
	private C c;
	public C getC(){
    
		return c;
	}
}
class C{
    
}
class A{
    
	private B b;
	public C getC(){
    
		return b.getC();
	}
}

This means A rely on B and C,B rely on C

Generalization relation

Generalization is actually inheritance , It is a special case of dependency

class B{
    
}
class A extends B{
    
	
}

here A generalization ( Inherit ) 了 B

Realization relationship

Realizing a relationship is actually A Realized B The abstract method in , It is A special case of dependency

interface B{
    }
class A implements B{
    }

here A Realized B

Connections

Correlation is actually The relationship between classes , He's a special case of dependency
The association is navigable ： That is, two-way relationship and one-way relationship
Relationships are multiple , Such as 1 It means a ,0… Express 0 One or more ,“0,1” Express 0 One or one ,“n,m” Express n To m Every one can ,m… At least m individual

class B{
    
}
class A{
    
	private B b;
}

This is a one-way Association

class B{
    
	private A a;
}
class A{
    
	private B b;
}

This is a two-way correlation

Aggregate relationship

An aggregate relationship is a relationship between the whole and the part , The whole and the part can be separated , Aggregation is a special case of association , So it has directionality and multiplicity （ Class , It can be for null, It can also be done through set Method to set the value , It means aggregation ）

class A{
    
	private B b;
	public void setB(B b){
    
		this.b = b;
	}
}

here B Aggregated in A

synthetic relation

The combinatorial relationship is also the relationship between the whole and the parts , But the whole and part cannot be separated , Because the whole is made up of parts , Indispensable ,（ Class , There is a non empty default value , Or the value is assigned in the constructor , Represents a combinatorial relationship ）

class A{
    
	private B b =  new B();
}

here B Combined in A