Operator & Assignments
1-:String Concatination Operator(+)
2-:Relational Operators(>,>=,<,<=)
3-:Equality Operators(==,!=)
String Concatenation operator
The only overloaded operator in java is (+) operator some time it accesses arithmetic addition operator some time it access String concatenation operator.
if at least one argument is String Type then + operator access concatenation operator and if both arguments are Number type then + operator access arithmetic addition operator.
Example-:
/*
String a="Sum";
int b=10,c=20,d=30;
System.out.print(a+b+c+d);//Sum102030
System.out.print(b+c+d+a);//60Sum
System.out.print(b+c+a+d);//30Sum30
System.out.print(b+a+c+d);//10Sum2030
*/
Example 2-:
consider the following declaration .
/*
String a="Sum";
int b=10,c=20,d=30;
a=b+c+d;//compile time error-:incompatible types found int required java.lang.String
a=a+b+c;//Sum1020
b=a+c+d;/compile time error-:incompatible types found String required int
b=b+c+d;//60
*/
Releational Operators
less than (<)
less than equal(<=)
grater than(>)
grater than equal(>=)
case1-:we can apply relational operator for every primitive type except boolean.
/*
System.out.print(10>7);//true
System.out.print(10>'a');//false
System.out.print('a'<976);//true
System.out.print('a'>'A');//true
System.out.print(true>false);//compile time error-:operator > cannot be applied to boolean,boolean
*/
case2-:we can't apply relational operator for Object types .
Example-:
/*
System.out.print("Sum123">"Sum");//compile time error-:Operator > can't be applied java.lang.String ,java.lang.String
*/
case4-:nesting of relational operators is not allowed otherwise we will get compile time error
/*
System.out.print(10<20<30);//compile time error-:operator can't be applied to boolean ,int
*/
Equality Operators
we can apply equality operators for every primitive type including the boolean type also.
Example-:
/*
System.out.print(10==20);//flalse
System.out.print('a'=='b');//false
System.out.print('a'==97.0);//true
System.out.print(false==false);//true
System.out.print(10==20);
*/
case1-:we can apply equality operator for object types also
for object references r1,r2
/*
if(r1==r2 )
return true
*/
if and only if both reference to same object(reference Comparison are address Comparison).
Example-:
/*
Thread t1=new Thread();
Thread t2=new Thread();
Thread t3=t1;
System.out.print(t1==t2);//false
System.out.print(t1==t3);//true
*/
Example2-:
if we apply an equality operator for object type then complusory there should be relation b/w argument types(either child to parent or parent to child or same type) otherwise we will get compile time error saying incomparable type java.lang.String and java.lang.Thread
/*
Thread t=new Thread();
Object o=new Object();
String s=new String("Java");
System.out.print(o==t);
System.out.print(o==s);
System.out.print(s==t)//compile time error-: incomparable type java.lang.String and java.lang.Thread
*/
Ouestion-: differention b/w ==operator and .equals() method?
ans-:in genral we can use (==)operator for refernce comprasion(address comprasion) and .equals() for containten comprasion.
Example-:
/*
String s=new String("Sum");
String str=new String("sub");
System.out.print(s==str);//false
System.out.print(s.equals(str));//true
*/
case 2-:for any object reference are ,
obj==null is always false but null==null is always true
