Comparing Wrappers

We can use == to compare primitives of compatible types.

int i1 = 500;
int i2 = 500;
System.out.println( i1 == i2 ); // true

With wrapper objects, == compares references, not contents.

Integer iw1 = Integer.valueOf(500);
Integer iw2 = Integer.valueOf(500);
System.out.println( iw1 == iw2 );     // false - references to different objects

• Just as with String, use equals to compare wrapper object contents.

System.out.println( iw1.equals(iw2) ); // true

Remember that we can only use == to compare references of compatible types - same class or class hierarchy.

• None of the wrappers extends another wrapper.

Long lw1 = Long.valueOf(500);
System.out.println( iw1 == lw1 ); // WILL NOT COMPILE: Incompatible operand types Integer and Long

NOTE: the wrapper class equals methods will only return true if both objects are of the exact same type.

int intVar = 500;
long longVar = 500;
System.out.println( intVar == longVar );          // true - int promoted to long and compared

Integer integerObj = Integer.valueOf(500);
Long longObj = Long.valueOf(500);
System.out.println( integerObj.equals(longObj) ); // false, even though both have value 500!

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