$BJ8;zNs$NHf3S(B

last-modified: Dec./23rd/2001

$BA0@a$G$O>r7o$N??56$K$h$C$F@)8f$NN.$l$,JQ$o$k(B if $BJ8$r>R2p$7$^$7$?!#K\@a$G$O!"J8;zNs$r(B equals() $B%a%=%C%I$r;H$C$FHf3S$7$?>r7o$r;H$C$F$_$^$9!#(B

== $B$H(B equals()

== $B$H(B equals() $B$N0c$$$K$D$$$F$O(B $BJ8;zNs$N@a(B $B$G>\$7$/@bL@$7$^$7$?!#K\@a$G$b4JC1$K@bL@$7$F$*$-$^$9!#(B

$BJ8;zNs$O(B String $B%/%i%9$r%$%s%9%?%s%92=$7$?%*%V%8%'%/%H$G$9$,!"(B String $B%/%i%9$K$O!"J8;zNs$H$7$FEy2A$G$"$k$+$I$&$+Hf3S$9$k0Y$N%a%=%C%I$,MQ0U$5$l$F$$$^$9!#(B

String $B%/%i%9$NJ8;zNsHf3S$N%a%=%C%I(B
equals()$BJ8;zNs$NFbMF$,Ey2A$G$"$k$+(B
equalsIgnoreCase()$BBgJ8;z!?>.J8;z$N6hJL$rL5;k(B
endsWith()$B$=$NJ8;z$G=*N;$9$k$+$I$&$+(B
startsWith()$B$=$NJ8;z$G3+;O$9$k$+$I$&$+(B

$B%=!<%9%3!<%I$N

String x,y,z;
x = new String("Hello");
y = new String("Hello");
z = new Streing("HELLO");
               System.out.println(x == y);	//false
          System.out.println(x.equals(y));	//true
          System.out.println(x.equals(z));	//false
System.out.println(x.equalsIgnoreCase(z));	//true

== $B$OJQ?t$K3JG<$5$l$?CM$,F1$8$b$N$G$"$k$+$I$&$+$rHf3S$7$^$9!#(B$B4pK\%G!<%?7?(B$B!J%W%j%_%F%#%V7?!K$N>l9g$OJQ?t$K$OCM$,J];}$5$l$F$$$k$N$G!"!VJQ?t$KBeF~$5$l$?CM$,F1$8$+$I$&$+!W$,??56$KBP1~$7$^$9!#(B$BJ8;zNs(B$B$N>l9g$O!"JQ?t$KBeF~$5$l$F$$$k$N$O!"%a%b%j>e$NJL$N>l=j$KB8:_$9$kJ8;zNs$r<1JL$9$k(B ID $B$G$9!#JL8D$KB8:_$9$kJ8;zNs$r<1JL$9$k(B ID $B$O0c$&$b$N$K$J$j$^$9$+$i!"JL8D$KDj5A$7$?J8;zNs$r;2>H$9$kJQ?t$K$O!"0[$J$k(B ID $B$,BeF~$5$l$F$$$^$9!#=>$C$F!"(B == $B$GHf3S$9$k$H56$K$J$j$^$9!#$3$l$OJ8;zNs$K8B$i$:!"%*%V%8%'%/%H0lHL$K$$$($k$3$H$G$9!#(B

equals() $B%a%=%C%I$GHf3S$9$k$N$O!"JQ?t$KBeF~$5$l$?(B ID $B$G$O$J$/!"$=$N(B ID $B$K$h$C$F<1JL$5$l$k%*%V%8%'%/%HF1;N$,Hf3S$5$l$^$9!#$=$N0Y!"JL$Nl9g$G$b!"%*%V%8%'%/%H$H$7$FEy2A$G$"$l$P??$,JV$j$^$9!#J8;zNs$N>l9g$O!"(BString $B7?%*%V%8%'%/%H$,J];}$7$F$$$kJ8;z$NG[Ns$,0lJ8;z$:$DHf3S$5$l$^$9!#(B

$BJ8;zNs$N>l9g$K$d$d$3$7$$$N$,!"

String str1 = "Hello";          	// $B5-K!(B1
String str2 = new String("Hello");	// $B5-K!(B2

$B5-K!(B1 $B$N>l9g$O2?EY5-=R$7$F$b!"F1$8%*%V%8%'%/%H$KBP$9$k;2>H$,JQ?t$K%3%T!<$5$l$^$9$,!"5-K!(B2 $B$N>l9g$O!"5-=R$9$kEY$KJL$N%*%V%8%'%/%H$,@8@.$5$l$F!"3F!9$N;2>H$,JQ?t$K%3%T!<$5$l$^$9!#$h$C$F!"5-K!(B1 $B$N>l9g$O!"(B== $B$G(B true $B$,JV$j$^$9$,!"5-K!(B2 $B$N>l9g$O(B false $B$,JV$j$^$9!#B>$K$b!"(B == $B$G(B false $B$,JV$k>l9g$r9M$($k$3$H$,$G$-$^$9!#$$$:$l$N>l9g$b!"(Bequals() $B$G$O(B true $B$,JV$k$N$G!"J8;zNs$NFbMF$rHf3S$9$k>l9g$O(B equals() $B%a%=%C%I$r;H$&$N$@$H3P$($F$/$@$5$$!#(B

$B%5%s%W%k(B

$B%3%^%s%I%i%$%s0z?t$+$i%f!<%6L>$r

IDCheck.java:

class IDCheck {
	public static void main(String[] args) {
		if (args[0].equals("sugai")) {
			System.out.println("$B%f!<%6$r3NG'$7$^$7$?!#(B");
		} else {
			System.out.println("$B$=$s$J%f!<%6$O$$$^$;$s!#(B");
		}
	}
}

if() $B$N>r7o<0$O!"J8;zNs$NEy2A@-Hf3S%a%=%C%I(B equals() $B$,;H$o$l$F$$$^$9!#(B String $B%/%i%9$r%$%s%9%?%s%92=$7$?%*%V%8%'%/%H(B args[0] $B$O!"%a%=%C%I(B equals() $B$rargs[0].equals() $B$O!"%*%V%8%'%/%H(B args[0] $B$N%a%=%C%I$G$"$j!"$3$N%*%V%8%'%/%H$H!"0z?t$G;}$C$F$$$kJ8;zNs$,Ey2A$G$"$k$+$I$&$+$rH=Dj$7!"(B true/false $B$rJV$7$^$9!#(B

$B$^$@%*%V%8%'%/%H$H%$%s%9%?%s%92=$K$D$$$F@bL@$7$F$$$J$$$N$G!"J,$+$i$J$/$F$bL`$b$G$9!#(B$BJ8;zNs(BA.equals("$BJ8;zNs(BB") $B$G!"J8;zNsHf3S$,=PMh$k$H$$$&$3$H$@$13P$($F$/$@$5$$!#(B

C:\Java>javac IDCheck.java
C:\Java>java IDCheck SUGAI
$B$=$s$J%f!<%6$O$$$^$;$s!#(B
C:\Java>java IDCheck sugai
$B%f!<%6$r3NG'$7$^$7$?!#(B

$B%a%=%C%I(B equals() $B$OBgJ8;z!?>.J8;z$N6hJL(B (Case Dependent) $B$r$7$^$9$N$G!"(B"SUGAI" $B$G$O(B true $B$K$J$j$^$;$s!#BgJ8;z!?>.J8;z$r6hJL$7$?$/$J$1$l$P!"(B equalsIgnoreCase() $B$rMxMQ$7$^$9!#(B

args[0].equalsIgnoreCase("sugai")

$BJ8;zNs$rA`:n$9$k%a%=%C%I$OB>$K$bBt;3$"$j$^$9$,!"(BString $B%/%i%9$N%a%=%C%I$G>R2p$7$^$9!JB?J,!K!#(B

$Br7oJ,4t$G$"$k!"(B switch $BJ8$K$D$$$F>R2p$7$^$9!#(B



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