In Java, there is no ready make API to compare two java.util.Set
1. Solution
Here’s my implementation, combine check size + containsAll :
SetUtils.java
package com.mkyong.core.utils;
import java.util.Set;
public class SetUtils {
public static boolean equals(Set<?> set1, Set<?> set2){
if(set1 == null || set2 ==null){
return false;
}
if(set1.size()!=set2.size()){
return false;
}
return set1.containsAll(set2);
}
}
2. Unit Test
Unit tests for the above SetUtils.java
TestSetUtils.java
package com.mkyong.core.utils;
import org.junit.Test;
import java.util.HashSet;
import java.util.Set;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
public class TestSetUtils {
@Test
public void test1() {
Set<String> test1 = new HashSet<>();
test1.add("a");
test1.add("b");
Set<String> test2 = new HashSet<>();
test2.add("b");
test2.add("c");
assertThat(SetUtils.equals(test1, test2), is(false));
}
@Test
public void test2() {
Set<String> test1 = new HashSet<>();
test1.add("a");
test1.add("b");
Set<String> test2 = new HashSet<>();
test2.add("a");
test2.add("b");
test2.add("c");
assertThat(SetUtils.equals(test1, test2), is(false));
}
@Test
public void test3() {
Set<String> test1 = new HashSet<>();
test1.add("a");
test1.add("b");
test1.add("c");
Set<String> test2 = new HashSet<>();
test2.add("a");
test2.add("b");
assertThat(SetUtils.equals(test1, test2), is(false));
}
//set ignore sequence
@Test
public void test4() {
Set<String> test1 = new HashSet<>();
test1.add("a");
test1.add("b");
Set<String> test2 = new HashSet<>();
test2.add("b");
test2.add("a");
assertThat(SetUtils.equals(test1, test2), is(true));
}
@Test
public void test5() {
Set<String> test1 = new HashSet<>();
test1.add("a");
Set<String> test2 = new HashSet<>();
test2.add("a");
assertThat(SetUtils.equals(test1, test2), is(true));
}
}
Run it, all unit tests will be passed.
References
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This is not needed. Look at AbstractSet.equals() it does this (and a bit better).
@Test
public void test6(){
Set test1=null;
Set test2=null;
assertTrue(SetUtils.equals(test1, test2));
}
this test fails, should it not pass ?
Look at the implementation of equals:
if(set1 == null || set2 ==null){
return false;
}
if you need the null valued two objects be equal, change the implementation.
Jake,
yes, implementation should be changed to address null
Thanks,
Charan