java - Why the output is different between JDK 1.4 and 1.5? -


i'm running code jdk 1.4 , 1.5 , different results. why case?

string str = ""; int test = 3;  str = string.valueof(test); system.out.println("str[" + str + "]\nequals result[" + (str == "3") + "]");  if (str == "3") {     system.out.println("if"); } else {     system.out.println("else"); }

outputs:

  • on jdk 1.4

    str[3] equals result[true] if

  • on jdk 1.5

    str[3] equals result[false] else

according this page, integer#tostring method (which called string#valueof(int)) implemented in 1.4:

public static string tostring(int i) {       switch(i) {           case integer.min_value: return "-2147483648";           case -3: return "-3";           case -2: return "-2";           case -1: return "-1";           case 0: return "0";           case 1: return "1";           case 2: return "2";           case 3: return "3";           case 4: return "4";           case 5: return "5";           case 6: return "6";           case 7: return "7";           case 8: return "8";           case 9: return "9";           case 10: return "10";       }       char[] buf = (char[])(perthreadbuffer.get());       int charpos = getchars(i, buf);       return new string(buf, charpos, 12 - charpos);   }

that explain result because string literal "3" interned , "3" == "3" returns true.

you can try 10 , 11 verify this.

note: mentioned, javadoc of integer#tostring not whether returned string interned or not both outputs in question equally valid.


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