字符串的比较函数
我们可以用“==”来比较字符串吗取决于我们使用的语言是否支持运算符重载
Java语言可能无法使用“==”来比较两个字符串。
在使用“==”的时候，实际上会比较这两个对象是否是同一个对象。
// "static void main" must be defined in a public class.
public class Test {
public static void main(String[] args) {
// initialize
String s1 = "Hello World";
System.out.println("s1 is \"" + s1 + "\"");
String s2 = s1;
System.out.println("s2 is another reference to s1.");
String s3 = new String(s1);
System.out.println("s3 is a copy of s1.");
// compare using '=='
System.out.println("Compared by '==':");
// true since string is immutable and s1 is binded to "Hello World"
System.out.println("s1 and \"Hello World\": " + (s1 == "Hello World"));
// true since s1 and s2 is the reference of the same object
System.out.println("s1 and s2: " + (s1 == s2));
// false since s3 is refered to another new object
System.out.println("s1 and s3: " + (s1 == s3));
// compare using 'equals'
System.out.println("Compared by 'equals':");
System.out.println("s1 and \"Hello World\": " + s1.equals("Hello World"));
System.out.println("s1 and s2: " + s1.equals(s2));
System.out.println("s1 and s3: " + s1.equals(s3));
// compare using 'compareTo'
System.out.println("Compared by 'compareTo':");
System.out.println("s1 and \"Hello World\": " + (s1.compareTo("Hello World") == 0));
System.out.println("s1 and s2: " + (s1.compareTo(s2) == 0));
System.out.println("s1 and s3: " + (s1.compareTo(s3) == 0));
}
}
通过上述代码可以看出比较字符串使用“equals”和“compareTo”一定没有问题。使用“==”的时候要谨慎。
