关于String操作的一个小例子

public class StringOperation {
private static final String A;

private static final String B;

static {
A = "ab";
B = "c";
}

public static void main(String[] args) {
//false
String s = "abc";
String s1 = "ab";
String s2 = "c";
String s3 = s1 + s2;
System.out.println(s==s3);

//true
String s4 = "abc";
System.out.println(s==s4);

//true
String s5 = "a" + "bc";
System.out.println(s==s5);

//false
String s6 = "a".concat("bc");
System.out.println(s==s6);

//true
final String s7 = "ab";
final String s8 = "c";
String s9 = s7 + s8;
System.out.println(s==s9);

//true
String s10 = s;
System.out.println(s==s10);

//false
String s11 = getPrefix() + "bc";
System.out.println(s==s11);

//false
String s12 = A + B;
System.out.println(s==s12);

//false
String s13 = new String(new char[] { 'a', 'b', 'c', 'd' });
String s14 = s13.intern();
System.out.println(s13==s14);
}

private static final String getPrefix() {
return "a";
}
}