java中字符串的比较

public class StringCompareTest {
public static void main(String[] args){
String s1 = "Hello";
String s2 = "Hello";
// assert pass, because both s1 and s2 point to the same const object.
assert s1 == s2;

String s3 = new String("World!");
String s4 = new String("World!");
// AssertionError, because s3 and s4 are different object
// assert s3 == s4;
assert s3 != s4;
// assert pass, equals are used to compare the contents of two strings.
assert s3.equals(s4);

String s5 = new String("");
// AssertionError, don't examine an empty string with '=='
// assert s5 == "";

}
}

javac StringCompareTest.java

java -ea StringCompareTest

-ea