Java String compare to determine Equality（Java String类型比较的三种方法）

java string compare can
be done in many ways as shown below. Depending on the type of java stringcompare you need, each of them is
used.

Comparing using the == Operator

The == operator is used when we have to compare the
String object references. If two String variables point to the same object in memory, the comparison returns true. Otherwise, the comparison returns false. Note that the ‘==’ operator does not compare the
content of the text present in
the String objects. It only compares the references the 2 Strings are pointing to. The following Program would print “The
strings are unequal” In the first case and “The strings are equal” in the second case.

public class StringComparision1 {

public static void main(String[] args) {
String name1 = "Bob";
String name2 = new String("Bob");
String name3 = "Bob";
// 1st case
if (name1 == name2) {
System.out.println("The strings are equal.");
} else {
System.out.println("The strings are unequal.");
}
// 2nd case
if (name1 == name3) {
System.out.println("The strings are equal.");
} else {
System.out.println("The strings are unequal.");
}
}
}

Comparing
using the equals Method

The
equals method is used when we need to compare the content of the text present in
the String objects.This
method returns true when two String objects hold the
same content (i.e. the same values). The following Program would print “The strings are unequal” In the first
case and “The strings are equal” in the second case.

public class StringComparision2 {

public static void main(String[] args) {
String name1 = "Bob";
String name2 = new String("Bob1");
String name3 = "Bob";
// 1st case
if (name1.equals(name2)) {
System.out.println("The strings are equal.");
} else {
System.out.println("The strings are unequal.");
}
// 2nd case
if (name1.equals(name3)) {
System.out.println("The strings are equal.");
} else {
System.out.println("The strings are unequal.");
}
}
}

Comparing
using the compareTo Method

The
compareTo method is used when we need to determine the order of
Strings lexicographically. It compares char values similar to the equals method. The compareTo method returns
a negative integer
if the first String object precedes the second string. It returns zero if the 2 strings being compared are equal. It returns a positive integer if the first String object follows the second string. The following Program would print “name2
follows name1” In the first case and “name1 follows name3” in the second case.

public class StringComparision3 {

public static void main(String[] args) {
String name1 = "bob";
String name2 = new String("cob");
String name3 = "Bob";
// 1st case
if (name1.compareTo(name2) == 0) {
System.out.println("The strings are equal.");
} else if (name1.compareTo(name2) < 0) {
System.out.println("name2 follows name1");
} else {
System.out.println("name1 follows name2");
}
// 2nd case. Comparing Ascii Uppercase will be smaller then Lower Case
if (name1.compareTo(name3) == 0) {
System.out.println("The strings are equal.");
} else if (name1.compareTo(name3) < 0) {
System.out.println("name3 follows name1");
} else {
System.out.println("name1 follows name3");
}
}
}

Reference： http://www.javabeginner.com/learn-java/java-string-comparison
END