Question

Suppose you have 2 Properties objects. One contains master properties, the other one is a target. Your job is to compare the two.

masterValue = masterProperties.getProperty(masterKey);


for (Properties targetFileProperty : targetFileList) {
   if (targetFileProperty.containsKey(masterKey)) {
   targetValue = targetFileProperty.getProperty(masterKey);

   if (masterValue.equals(targetValue)) { //<---- this is where the problem is
      // do something clever
   } else {
      // do something clever

The problem i am facing in this example is this:

When master key is “A” and master value is “10” and target key is “A” and “target key is ” 10 “, code above thinks that these are the same. In other words it is either trimming or ignoring white space.

Can you eithe point out an error in my logic or suggest a better way to assert that white space is not to be ignored? Thank you.

Answer 1

java.util.Properties inherits its equals(Object) from Hashtable, which implements Map equality:

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps m1 and m2 represent the same mappings if m1.entrySet().equals(m2.entrySet()). This ensures that the equals method works properly across different implementations of the Map interface.

So if you want to compare if two Properties contain the same keys and values, you can just do props1.equals(props2).

As for your problem, I don’t think you’ve identified the real problem. " 10 ".equals("10") is definitely false. The problem may be that the strings were trimmed before entered as values to the Properties (you can print the values that you’re comparing to see if this is indeed the case).

If the whitespaces are significant, you must escape it in the properties file. Here’s a snippet to show how it’s done:

    Properties p = new Properties();
    p.put("X", "   ");
    p.store(System.out, "test");

This prints (I’ve substituted _ for space for clarity):

#test
#Mon Jun 21 22:20:04 ICT 2010
X=\___