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Regarding Object Comparison


Regarding Object Comparison

By : user220198
Date : October 26 2020, 11:51 AM
This might help you You need to implement the equals() and hashCode() methods to implement object equality in Java:
code :


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Value comparison vs. Object reference comparison

Value comparison vs. Object reference comparison


By : Toma
Date : March 29 2020, 07:55 AM
To fix the issue you can do x == y is a value comparison (because y is a primitive type), so 1000==1000 -> true.
x == z is an object reference comparison - object x is not an object z. They hold the same values, but they are still two completely different objects. So if you compare them you get false.
Performance comparison(in the terms of heap size) whether to use collection object or Java transfer object

Performance comparison(in the terms of heap size) whether to use collection object or Java transfer object


By : Jeff
Date : March 29 2020, 07:55 AM
seems to work fine Which one having less performance issue (in the terms of heap size). , Transfer object is much more economical, try this test
code :
public class Test1 {
    int i1 = 1;
    int i2 = 1;

    public static void main(String[] args) throws Exception {
        Runtime rt = Runtime.getRuntime();
        long m0 = rt.totalMemory() - rt.freeMemory();
        Map m = new HashMap();
        m.put("i1", 1);
        m.put("i2", 1);
        //Test1 t1 = new Test1();  
        long m1 = rt.totalMemory() - rt.freeMemory();
        System.out.println(m1 - m0);
    }
}
JS function "Deep comparison". Object comparison

JS function "Deep comparison". Object comparison


By : Anthony Marini
Date : March 29 2020, 07:55 AM
This might help you I wanted to implement JS function "Deep comparison" and encounter on one interesting feature.
code :
   for (let i = 0; i < arrKeysObjA.length; i++) {
        arrValuesObjA.push( objA[ arrKeysObjA[i] ] );
    }

    for (let i = 0; i < arrKeysObjB.length; i++) {
        arrValuesObjB.push( objA[ arrKeysObjB[i] ] );
    }
Generic object comparison method with a variable number of method references for comparison

Generic object comparison method with a variable number of method references for comparison


By : Veha Suwatphisankij
Date : March 29 2020, 07:55 AM
Any of those help I often have to compare to instances of a certain type for equality, but I do not need to compare everything, but only certain fields. I usually do it like this: , I managed to come up with something that seems to work:
code :
public static <T extends BaseType> boolean areFieldsEqual(T left, T right, Function<T,? extends Comparable>... fields)
{
    if (fields.length < 1) {
        return true;
    }
    Comparator<T> c = Comparator.comparing(fields[0]);
    for (int i = 1; i < fields.length; i++) {
        c = c.thenComparing (fields[i]);
    }
    return c.compare(left, right) == 0;
}
class BaseType {
    String x;
    int y;
    public BaseType (String x, int y) {
        this.x=x;
        this.y=y;
    }
    String getX () {return x;}
    int getY () { return y;}
}

class SubType extends BaseType {
    String z;

    public SubType (String x, int y,String z) {
        super(x,y);
        this.z=z;
    }
    String getZ () {return z;}
}
BaseType one = new BaseType("some",1);
BaseType two = new BaseType("some",2);
SubType three = new SubType("some",1,"else");
SubType four = new SubType("some",2,"else");
System.out.println (areFieldsEqual(one,two,BaseType::getX,BaseType::getY));
System.out.println (areFieldsEqual(three,four,SubType::getZ,BaseType::getX));
false
true
Javascript / Lodash deep comparison object from an array of object

Javascript / Lodash deep comparison object from an array of object


By : user3019599
Date : March 29 2020, 07:55 AM
I wish this helpful for you You can easily do that by using intersectionWith - it accepts a custom comparator for your elements. The easiest way is to convert the object into an array of entries using toPairs and then compare those with isEqual. The intersection would then be an array containing pairs of attribute and value, so you can then convert it back to an object using fromPairs
code :
let arr = [
  {
    abcdef: {name: 'Robin', uid: '123'},
    ghijkl: {name: 'Simon', uid: '456'}
  },
  {
    mnopqr: {name: 'Alex', uid: '789'},
    abcdef: {name: 'Robin', uid: '123'}
  },
  {
    abcdef: {name: 'Robin', uid: '123'},
    stuvwx: {name: 'Julianna', uid: '111'},
    yzxwuv: {name: 'Elon', uid: '007'}
  }
];

const inputPairs = arr.map(_.toPairs);

const resultPairs = _.intersectionWith(...inputPairs, _.isEqual);

const resultObject = _.fromPairs(resultPairs);

console.log(resultObject);
<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.15/lodash.min.js"></script>
let arr = [ { abcdef: {name: 'Robin', uid: '123'}, ghijkl: {name: 'Simon', uid: '456'} }, { mnopqr: {name: 'Alex', uid: '789'}, abcdef: {name: 'Robin', uid: '123'} }, { abcdef: {name: 'Robin', uid: '123'}, stuvwx: {name: 'Julianna', uid: '111'}, yzxwuv: {name: 'Elon', uid: '007'} } ];

const resultObject = _(arr)
  .map(_.toPairs)
  .thru(pairs => _.intersectionWith(...pairs, _.isEqual))
  .fromPairs()
  .value();

console.log(resultObject);
<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.15/lodash.min.js"></script>
const {spread, intersectionWith, isEqual, flow, map, toPairs, fromPairs} = _;

let arr = [ { abcdef: {name: 'Robin', uid: '123'}, ghijkl: {name: 'Simon', uid: '456'} }, { mnopqr: {name: 'Alex', uid: '789'}, abcdef: {name: 'Robin', uid: '123'} }, { abcdef: {name: 'Robin', uid: '123'}, stuvwx: {name: 'Julianna', uid: '111'}, yzxwuv: {name: 'Elon', uid: '007'} } ];

const process = flow(
  map(toPairs), 
  spread(intersectionWith(isEqual)), 
  fromPairs
);

const resultObject = process(arr);

console.log(resultObject);
<script src="https://cdn.jsdelivr.net/g/lodash@4(lodash.min.js+lodash.fp.min.js)"></script>
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