String | StringBuffer | |
---|---|---|
文字列の変更はできません。 | 変更可能です。 | |
String s = "Hello"; |
StringBuffer sb = new StringBuffer("Hello"); |
|
s += " World"; |
sb.append(" World"); |
|
String s1 = new String("Hello"); String s2 = new String("Hello"); : s1 == s2 ... false s1.equals(s2) ... true : String s3 = s1; s1 += " World"; : s1 ... "Hello World" s3 ... "Hello" |
StringBuffer sb1 = new StringBuffer("Hello"); StringBuffer sb2 = new StringBuffer("Hello"); : sb1 == sb2 ... false sb1.equals(sb2) ... false : StringBuffer sb3 = sb1; sb1.append(" World"); : sb1 ... "Hello World" sb3 ... "Hello World" |
- public class StringBuffer50 {
- public static void main(String[] args) {
- StringBuffer sb1 = new StringBuffer("Hello");
- StringBuffer sb2 = sb1;
- sb1.append(" World!");
- System.out.println("sb1 == sb2 ? " + (sb1 == sb2));
- }
- }
□ 実行結果
$ java StringBuffer50 sb1 == sb2 ? true
- public class StringBuffer51 {
- public static void main(String[] args) {
- StringBuffer sb1 = new StringBuffer("Hello");
- System.out.println(" sb1 = " + sb1);
- sb1.append(" World!");
- System.out.println(" sb1.append(\" World!\") = " + sb1);
- sb1.insert(5, " Java");
- System.out.println(" sb1.insert(5, \" Java\") = " + sb1);
- sb1.replace(6, 10, "Servlet");
- System.out.println("sb1.replace(6, 10, \"Servlet\") = " + sb1);
- sb1.reverse();
- System.out.println(" sb1.reverse() = " + sb1);
- }
- }
□ 実行結果
$ java StringBuffer51 sb1 = Hello sb1.append(" World!") = Hello World! sb1.insert(5, " Java") = Hello Java World! sb1.replace(6, 10, "Servlet") = Hello Servlet World! sb1.reverse() = !dlroW telvreS olleH
- public class ArrayUtil {
- static String toString(int[] a) {
- StringBuffer sb = new StringBuffer("[");
- for (int i = 0; i < a.length; i++) {
- if (i != a.length -1) {
- sb.append(a[i] + ", ");
- } else {
- sb.append(a[i]);
- }
- }
- sb.append("]");
- return sb.toString();
- }
- }
- public class StringBuffer10 {
- public static void main(String[] args) {
- StringBuffer sb = new StringBuffer();
- for (int i = 0; i < args.length; i++) {
- // ここにコードを書いてください。
- }
- System.out.println(sb);
- }
- }
□ 実行結果
$ java StringBuffer10 Hello Java World World Java Hello
□ 実行結果
実行結果 $ java StringBuffer11 Hello Java World dlroW avaJ olleH
- public class StringBuffer20 {
- public static void main(String[] args) {
- StringBuffer sb = new StringBuffer(args[0]);
- int i;
- while ((i = sb.indexOf(args[1])) > -1) {
- // ここにコードを書いてください。
- }
- System.out.println(sb);
- }
- }
□ 実行結果
$ java StringBuffer20 "hello world, java, and hello to you all" hello hi hi world, java, and hi to you all