这是我的代码:
String str = "just_a_string";
System.out.println("]" + str + "[");
System.out.println("]" + str.replace("", "") + "[");
System.out.println("]" + str.substring(5) + "[");
System.out.println("]" + str.substring(5).replace("", "") + "[");
System.out.println("]" + str.substring(3, 8) + "[");
System.out.println("]" + str.substring(3, 8).replace("", "") + "[");
System.out.println("]" + "sdajndan".substring(5).replace("", "") + "[");
这是输出
05-09 19:09:20.570: I/System.out(23801): ]just_a_string[
05-09 19:09:20.570: I/System.out(23801): ]just_a_string[
05-09 19:09:20.570: I/System.out(23801): ]a_string[
05-09 19:09:20.570: I/System.out(23801): ]a_s[ **
05-09 19:09:20.570: I/System.out(23801): ]t_a_s[
05-09 19:09:20.570: I/System.out(23801): ]t_[ **
05-09 19:09:20.570: I/System.out(23801): ][ **
显然,标有**的行是意外的。
此问题发生在我的 Android 手机 A(LG P920 Optimus 3D,Android 2.3.3)上。当我在 Android 手机 B(LG E720 Optimus Chic,Android 2.2)上进行测试时,它停止了。我猜它会陷入无限循环。
我已经在两部手机上进行了测试,分别使用 Java 1.5
和 1.6
。两者分别导致相同的行为。
我还在同一个 Eclipse 上使用 Java 项目测试了 1.5
、1.6
和 1.7
。正如预期的那样,他们的所有输出都是正确的。
我想知道这可能是针对字符串的 backing array 实现 String.replace(“”, “”)
的设备特定问题。 .
您能帮我在您的设备上进行测试吗?
有人可以向我提供 String.replace(CharSequence, CharSequence)
方法的 Android 源代码吗? (就像 docjar 中的内容)
非常感谢!
我对代码做了一些修改,所以它也可以在Android设备上显示。 (无论如何,这只是相同的代码)。
在我的手机 A 和手机 B 上进行了测试。如上所述,行为仍然相同。
package com.example.testprojectnew;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class MainActivity extends Activity {
String output_text = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String str = "just_a_string";
process("1]" + str + "[");
process("2]" + str.replace("", "") + "[");
process("3]" + str.substring(5) + "[");
process("4]" + str.substring(5).replace("", "") + "[");
process("5]" + str.substring(3, 8) + "[");
process("6]" + str.substring(3, 8).replace("", "") + "[");
process("7]" + "sdajndan".substring(5).replace("", "") + "[");
output_text = output_text.concat("\n\nLines (1 & 2), (3 & 4), (5 & 6), should be the same.");
((TextView) findViewById(R.id.a_string)).setText(output_text);
}
private void process(String str) {
System.out.println(str);
output_text = output_text.concat(str).concat("\n");
}
}
最佳答案
宾果游戏!我发现了这个错误!
感谢@izht提供source code的链接。我已经找到了有关此问题的错误。
这只发生在字符串 backing array 时具有与实际字符串不同(更长)的值。特别是,当String.offset
(私有(private)变量)大于零时。
修复方法如下:
public String replace(CharSequence target, CharSequence replacement) {
if (target == null) {
throw new NullPointerException("target == null");
}
if (replacement == null) {
throw new NullPointerException("replacement == null");
}
String targetString = target.toString();
int matchStart = indexOf(targetString, 0);
if (matchStart == -1) {
// If there's nothing to replace, return the original string untouched.
return this;
}
String replacementString = replacement.toString();
// The empty target matches at the start and end and between each character.
int targetLength = targetString.length();
if (targetLength == 0) {
int resultLength = (count + 2) * replacementString.length();
StringBuilder result = new StringBuilder(resultLength);
result.append(replacementString);
// for (int i = offset; i < count; ++i) { // original, bug
for (int i = offset; i < (count + offset); ++i) { // fix
result.append(value[i]);
result.append(replacementString);
}
return result.toString();
}
StringBuilder result = new StringBuilder(count);
int searchStart = 0;
do {
// Copy characters before the match...
result.append(value, offset + searchStart, matchStart - searchStart);
// Insert the replacement...
result.append(replacementString);
// And skip over the match...
searchStart = matchStart + targetLength;
} while ((matchStart = indexOf(targetString, searchStart)) != -1);
// Copy any trailing chars...
result.append(value, offset + searchStart, count - searchStart);
return result.toString();
}
我不确定为什么 Android 必须以这种方式更改(并且错误地更改)replace()
。原来的Java实现没有这个问题。
顺便问一下,现在怎么样?我可以用它做什么? (除了格外小心地使用 replace()
或扔掉我的 Android 手机:-/)
顺便说一句,我很确定我的 LG E720 Optimus Chic (Android 2.2) 使用的源代码与 that one 不同。 。当 String.replace()
目标字符串为空时,它会不断停止(怀疑是无限循环)。最近我发现它抛出此错误消息:
05-10 16:41:13.155: E/AndroidRuntime(9384): FATAL EXCEPTION: main
05-10 16:41:13.155: E/AndroidRuntime(9384): java.lang.OutOfMemoryError
05-10 16:41:13.155: E/AndroidRuntime(9384): at java.lang.AbstractStringBuilder.enlargeBuffer(AbstractStringBuilder.java:97)
05-10 16:41:13.155: E/AndroidRuntime(9384): at java.lang.AbstractStringBuilder.append0(AbstractStringBuilder.java:157)
05-10 16:41:13.155: E/AndroidRuntime(9384): at java.lang.StringBuilder.append(StringBuilder.java:217)
05-10 16:41:13.155: E/AndroidRuntime(9384): at java.lang.String.replace(String.java:1497)
05-10 16:41:13.155: E/AndroidRuntime(9384): at com.example.testprojectnew.MainActivity.onCreate(MainActivity.java:22)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.os.Handler.dispatchMessage(Handler.java:99)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.os.Looper.loop(Looper.java:123)
05-10 16:41:13.155: E/AndroidRuntime(9384): at android.app.ActivityThread.main(ActivityThread.java:4627)
05-10 16:41:13.155: E/AndroidRuntime(9384): at java.lang.reflect.Method.invokeNative(Native Method)
05-10 16:41:13.155: E/AndroidRuntime(9384): at java.lang.reflect.Method.invoke(Method.java:521)
05-10 16:41:13.155: E/AndroidRuntime(9384): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
05-10 16:41:13.155: E/AndroidRuntime(9384): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
05-10 16:41:13.155: E/AndroidRuntime(9384): at dalvik.system.NativeStart.main(Native Method)
再想一想,如果那个 for 循环是 的错误。应该是编译时的问题。为什么它在不同手机(不同版本的 Android)中会有不同的表现?
完整的解决方法
得到an update来自 Google,他们已经修补了它,并将更正它 in the future release .
同时,我编写了一个基于 their code 的修补方法。 :
(这是必要的,因为(1)我们仍然需要等待正确的版本,(2)我们需要照顾没有进行固定更新的设备)
/** Patch for the String.replace(CharSequence target, CharSequence replacement),
* because the original is buggy when CharSequence target is empty, i.e. "".
* Patched by Google Android: https://android-review.googlesource.com/58393
*/
public static String replacePatched(final String string, final CharSequence target, final CharSequence replacement) {
if (target == null) {
throw new NullPointerException("target == null");
}
if (replacement == null) {
throw new NullPointerException("replacement == null");
}
final String targetString = target.toString();
int matchStart = string.indexOf(targetString, 0);
if (matchStart == -1) {
// If there's nothing to replace, return the original string untouched.
return new String(string);
}
final char[] value = string.toCharArray(); // required in patch
final int count = value.length; // required in patch
final String replacementString = replacement.toString();
// The empty target matches at the start and end and between each character.
if (targetString.length() == 0) {
// The result contains the original 'count' characters, a copy of the
// replacement string before every one of those characters, and a final
// copy of the replacement string at the end.
final StringBuilder result = new StringBuilder(count + (count + 1) * replacementString.length());
result.append(replacementString);
for (int i = 0; i < count; ++i) {
result.append(value[i]);
result.append(replacementString);
}
return new String(result); // StringBuilder.toString() does not give exact length
}
final StringBuilder result = new StringBuilder(count);
int searchStart = 0;
do {
// Copy characters before the match...
result.append(value, searchStart, matchStart - searchStart);
// Insert the replacement...
result.append(replacementString);
// And skip over the match...
searchStart = matchStart + targetString.length();
} while ((matchStart = string.indexOf(targetString, searchStart)) != -1);
// Copy any trailing chars...
result.append(value, searchStart, count - searchStart);
return new String(result); // StringBuilder.toString() does not give exact length
}
详细版本:
/** Patch for the String.replace(CharSequence target, CharSequence replacement),
* because the original is buggy when CharSequence target is empty, i.e. "".
* Patched by Google Android: https://android-review.googlesource.com/58393
*/
public static String replacePatched(final String string, final CharSequence target, final CharSequence replacement) {
if (target == null) {
throw new NullPointerException("target == null");
}
if (replacement == null) {
throw new NullPointerException("replacement == null");
}
// String targetString = target.toString(); // original
final String targetString = target.toString();
// int matchStart = indexOf(targetString, 0); // original
int matchStart = string.indexOf(targetString, 0);
if (matchStart == -1) {
// If there's nothing to replace, return the original string untouched.
// return this; // original
return new String(string);
}
final char[] value = string.toCharArray(); // required in patch
final int count = value.length; // required in patch
// String replacementString = replacement.toString(); // original
final String replacementString = replacement.toString();
// The empty target matches at the start and end and between each character.
// int targetLength = targetString.length(); // original
// if (targetLength == 0) { // original
if (targetString.length() == 0) {
// int resultLength = (count + 2) * replacementString.length(); // original
// // The result contains the original 'count' characters, a copy of the
// // replacement string before every one of those characters, and a final
// // copy of the replacement string at the end.
// int resultLength = count + (count + 1) * replacementString.length(); // patched by Google Android
// StringBuilder result = new StringBuilder(resultLength); // original
final StringBuilder result = new StringBuilder(count + (count + 1) * replacementString.length());
result.append(replacementString);
// for (int i = offset; i < count; ++i) { // original
// int end = offset + count; // patched by Google Android
// for (int i = offset; i != end; ++i) { // patched by Google Android
for (int i = 0; i < count; ++i) {
result.append(value[i]);
result.append(replacementString);
}
// return result.toString(); // original
return new String(result); // StringBuilder.toString() does not give exact length
}
// StringBuilder result = new StringBuilder(count); // original
final StringBuilder result = new StringBuilder(count);
int searchStart = 0;
do {
// Copy characters before the match...
// result.append(value, offset + searchStart, matchStart - searchStart); // original
result.append(value, searchStart, matchStart - searchStart);
// Insert the replacement...
result.append(replacementString);
// And skip over the match...
// searchStart = matchStart + targetLength; // original
searchStart = matchStart + targetString.length();
// } while ((matchStart = indexOf(targetString, searchStart)) != -1); // original
} while ((matchStart = string.indexOf(targetString, searchStart)) != -1);
// Copy any trailing chars...
// result.append(value, offset + searchStart, count - searchStart); // original
result.append(value, searchStart, count - searchStart);
// return result.toString(); // original
return new String(result); // StringBuilder.toString() does not give exact length
}
关于java - 安卓有bug吗? : String. substring(5).replace (“” , “” )//空字符串,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16475317/