Compares the value of the string object (or a substring) to the sequence of characters specified by its arguments. The compared string is the value of the string object or -if the signature used has a pos and a len parameters- the substring that begins at its character in position pos and spans len characters. This string is compared to a comparing string…
Compares two specified objects and returns an integer that indicates their relative position in the sort order.
Compare strings using ordinal (binary) sort rules and ignoring the case of the strings being compared. Examples The following example compares four sets of words by using each member of the StringComparison enumeration.
Learn how to compare and order string values, with or without case, with or without culture specific ordering
I’ve been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug. Is == bad? When should
== tests for reference equality (whether they are the same object). .equals() tests for value equality (whether they are logically „equal“). Objects.equals() checks for null before calling .equals() so you don’t have to (available as of JDK7, also available in Guava ). String.contentEquals() compares the content of the String with the content of any CharSequence (available since Java 1.5). Consequently, if you want to test whether two strings have the same value you will probably want to use Objects.equals() . // These two have the same value
new String(„test“).equals(„test“) // –> true
// but they are not the same object
new String(„test“) == „test“ // –> false
// neither are these
new String(„test“) == new String(„test“) // –> false
// but these are because literals are interned by
// the compiler and thus refer to the same object
„test“ == „test“ // –> true
// string literals are concatenated by the compiler
// and the results are interned.
„test“ == „te“ + „st“ // –> true
// but you should really just call Objects.equals()
Objects.equals(„test“, new String(„test“)) // –> true
Objects.equals(null, „test“) // –> false
Objects.equals(null, null) // –> true
You almost always want to use Objects.equals() . In the rare situation where you know you’re dealing with interned strings, you can use == . From JLS 3.10.5. String Literals : Moreover, a string literal always refers to the same instance of class String . This is because string literals – or, more generally, strings that are the values of constant expressions ( §15.28 ) – are „interned“ so as to share unique instances, using the method String.intern . Similar examples can also be found in JLS 3.10.5-1 .Best answer · 4972== tests object references, .equals() tests the string values. Sometimes it looks as if == compares values, because Java does some behind-the-scenes stuff to make sure identical in-line strings are actually the same object. For example: String fooString1 = new String(„foo“);
String fooString2 = new String(„foo“);
// Evaluates to false
fooString1 == fooString2;
// Evaluates to true
// Evaluates to true, because Java uses the same object
„bar“ == „bar“;
But beware of nulls! == handles null strings fine, but calling .equals() from a null string will cause an exception: String nullString1 = null;
String nullString2 = null;
// Evaluates to true
System.out.print(nullString1 == nullString2);
// Throws a NullPointerException
So if you know that fooString1 may be null, tell the reader that by writing System.out.print(fooString1 != null && fooString1.equals(„bar“));
The following is shorter, but it’s less obvious that it checks for null (from Java 7): System.out.print(Objects.equals(fooString1, „bar“));628== compares Object references. .equals() compares String values. Sometimes == gives illusions of comparing String values, as in following cases: String a=“Test“;
if(a==b) ===> true
This is because when you create any String literal, the JVM first searches for that literal in the String pool, and if it finds a match, that same reference will be given to the new String. Because of this, we get: (a==b) ===> true String Pool
b —————–> „test“ false
In this case for new String(„test“) the statement new String will be created on the heap, and that reference will be given to b , so b will be given a reference on the heap, not in String pool. Now a is pointing to a String in the String pool while b is pointing to a String on the heap. Because of that we get: if(a==b) ===> false. String Pool
„test“ <——————– a
String b=new String(„test“);
if(a.equals(b)) ===> true
So using .equals() is always better.398The == operator checks to see if the two strings are exactly the same object. The .equals() method will check if the two strings have the same value.203Strings in Java are immutable. That means whenever you try to change/modify the string you get a new instance. You cannot change the original string. This has been done so that these string instances can be cached. A typical program contains a lot of string references and caching these instances can decrease the memory footprint and increase the performance of the program. When using == operator for string comparison you are not comparing the contents of the string, but are actually comparing the memory address. If they are both equal it will return true and false otherwise. Whereas equals in string compares the string contents. So the question is if all the strings are cached in the system, how come == returns false whereas equals return true? Well, this is possible. If you make a new string like String str = new String(„Testing“) you end up creating a new string in the cache even if the cache already contains a string having the same content. In short „MyString“ == new String(„MyString“) will always return false. Java also talks about the function intern() that can be used on a string to make it part of the cache so „MyString“ == new String(„MyString“).intern() will return true. Note: == operator is much faster than equals just because you are comparing two memory addresses, but you need to be sure that the code isn’t creating new String instances in the code. Otherwise you will encounter bugs.154String a = new String(„foo“);
String b = new String(„foo“);
System.out.println(a == b); // prints false
System.out.println(a.equals(b)); // prints true
Make sure you understand why. It’s because the == comparison only compares references; the equals() method does a character-by-character comparison of the contents. When you call new for a and b , each one gets a new reference that points to the „foo“ in the string table. The references are different, but the content is the same.132Yea, it’s bad == means that your two string references are exactly the same object. You may have heard that this is the case because Java keeps sort of a literal table (which it does), but that is not always the case. Some strings are loaded in different ways, constructed from other strings, etc., so you must never assume that two identical strings are stored in the same location. Equals does the real comparison for you.114Yes, == is bad for comparing Strings (any objects really, unless you know they’re canonical). == just compares object references. .equals() tests for equality. For Strings, often they’ll be the same but as you’ve discovered, that’s not guaranteed always.110Java have a String pool under which Java manages the memory allocation for the String objects. See String Pools in Java When you check (compare) two objects using the == operator it compares the address equality into the string-pool. If the two String objects have the same address references then it returns true , otherwise false . But if you want to compare the contents of two String objects then you must override the equals method. equals is actually the method of the Object class, but it is Overridden into the String class and a new definition is given which compares the contents of object. Example:
But mind it respects the case of String. If you want case insensitive compare then you must go for the equalsIgnoreCase method of the String class. Let’s See: String one = „HELLO“;
String two = „HELLO“;
String three = new String(„HELLO“);
String four = „hello“;
one == two; // TRUE
one == three; // FALSE
one == four; // FALSE
one.equals(two); // TRUE
one.equals(three); // TRUE
one.equals(four); // FALSE
one.equalsIgnoreCase(four); // TRUE104.equals() compares the data in a class (assuming the function is implemented).
== compares pointer locations (location of the object in memory). == returns true if both objects (NOT TALKING ABOUT PRIMITIVES) point to the SAME object instance.
.equals() returns true if the two objects contain the same data equals() Versus == in Java That may help you.92
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The Compare (String, String, CultureInfo, CompareOptions) method does not consider such characters when it performs a culture-sensitive comparison. To recognize ignorable characters in your comparison, supply a value of CompareOptions .
Java String compare We can compare string in java on the basis of content and reference. It is used in authentication (by equals() method), sorting (by compareTo() method), reference matching (by == operator) etc.
The String.CompareTo method compares the string that the current string object encapsulates to another string or object. The return values of this method are identical to the values returned by the String.Compare method in the previous table.
However, if the two strings compare equal to the end of one string, and the other string has characters remaining, then the string with remaining characters is considered greater. The return value is the result of the last comparison performed.
In the C Programming Language, the strcmp function returns a negative, zero, or positive integer depending on whether the object pointed to by s1 is less than, equal to, or greater than the object pointed to by s2.