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interface inheritance of same method

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Last Modified: 2019-01-10
6. Multiple inheritance of state is not allowed:
Remember that Java does not allow a class inherits two or more classes directly. To understand why multiple inheritance is not allowed, consider the following example:
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public class A {
    public void methodA() {
 
    }
 
    public void foo() {
 
    }
}
 
 
public class B {
    public void methodB() {
 
    }
 
    public void foo() {
 
    }
}
Suppose that we want to write a class C that extends both A and B like this:
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public class C extends A, B {
    public void methodC() {
        foo();
    }
}
As you can see, both A and B has a method called foo(), so which foo() method the class C invokes exactly? from A or B? This case is ambiguous hence Java does not allow.
 
7. Multiple inheritance of type is allowed:
This means Java does allow multiple inheritance between interfaces. For example:
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public interface X {
    public void methodX();
}
 
public interface Y {
    public void methodY();
}
 
public interface Z extends X, Y {
    public void methodZ();
}
This is allowed because interfaces do not have concrete methods, thus there is no ambiguity.
Likewise, we can have a class implements multiple interfaces:
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public class Sub implements X, Y, Z {
    public void methodX() { }
 
    public void methodY() { }
 
    public void methodZ() { }
}

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if both Interface X and Interface Y has same method called methodAB what happens?


6. Multiple inheritance of state is not allowed:
Remember that Java does not allow a class inherits two or more classes directly. To understand why multiple inheritance is not allowed, consider the following example:
1
2
3
4
5
6
7
8
9
10
11
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13
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20
public class A {
    public void methodA() {
 
    }
 
    public void foo() {
 
    }
}
 
 
public class B {
    public void methodB() {
 
    }
 
    public void foo() {
 
    }
}
Suppose that we want to write a class C that extends both A and B like this:
1
2
3
4
5
public class C extends A, B {
    public void methodC() {
        foo();
    }
}
As you can see, both A and B has a method called foo(), so which foo() method the class C invokes exactly? from A or B? This case is ambiguous hence Java does not allow.
 
7. Multiple inheritance of type is allowed:
This means Java does allow multiple inheritance between interfaces. For example:
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public interface X {
    public void methodAB();
}
 
public interface Y {
    public void methodAB();
}
 
public interface Z extends X, Y {
    public void methodZ();
}
This is allowed because interfaces do not have concrete methods, thus there is no ambiguity.
Likewise, we can have a class implements multiple interfaces:
1
2
3
4
5
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public class Sub implements X, Y, Z {
    public void methodX() { }
 
    public void methodY() { }
 
    public void methodZ() { }
}

Open in new window


in this case

public interface Z extends X, Y {
    public void methodAB();
}

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in above case Z gets X method or Y method


something like below
package MultipleInheritanceType;
public interface X {
    public void methodAB();
}

package MultipleInheritanceType;
public interface Y {
    public void methodAB();
}


package MultipleInheritanceType;
public interface Z extends X, Y {
    public void methodABC();
}

package MultipleInheritanceType;
public class Sub implements X, Y, Z {

	@Override
	public void methodABC() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void methodAB() {
		// TODO Auto-generated method stub
		
	}
    /*public void methodX() { }
 
    public void methodY() { }
 
    public void methodZ() { }*/
} 

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what is difference between inheritance of state and  type
Please advise
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