宾果！我找到了这个错误！

Question

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**的行是意料之外的。

这个问题发生在我的Android手机A（LG P920 Optimus 3D，Android 2.3.3）上。当我在我的Android手机B（LG E720 Optimus Chic，Android 2.2）上测试时，它停止了。我猜它会遇到无限循环。

我已经在两部手机上测试了Java 1.5和1.6。两者分别导致相同的行为。

我还在我的同一个Eclipse上使用 Java 项目测试了1.5，1.6和1.7。正如预期的那样，它们的所有输出都是正确的。

我想知道这可能是针对字符串backing array实施String.replace(“”, “”)的设备特定问题。

你能帮我测试你的设备吗？

有人可以请我提供String.replace(CharSequence, CharSequence)方法的Android源代码吗？（就像docjar）

中的内容

非常感谢！

我已经修改了一下代码，因此它也可以在Android设备上显示。（无论如何它都是相同的代码。）

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");
    }
}

Answer 1

宾果！我找到了这个错误！

感谢@izht提供source code的链接。我找到了有关此问题的错误。

仅当String的backing array具有与实际String不同（更长）的值时才会发生这种情况。特别是，当String.offset（私有变量）大于零时。

以下是修复：

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必须以这种方式改变（并错误地改变）replace()。原始的Java实现没有这个问题。

顺便说一句，现在怎么办？我该怎么办？（除了特别小心使用replace()，或扔掉我的Android手机： - /）

顺便说一下，我确信我的LG E720 Optimus Chic（Android 2.2）使用的源代码与that one不同。它使用空目标字符串在String.replace()上停止（怀疑无限循环）。最近我发现它抛出了这个错误信息：

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循环的东西是那个错误。它应该是一个编译时问题。为什么它会在不同的手机（不同版本的Android）中采取不同的行为？

完整解决方法

来自Google的an update，他们已对其进行了修补，并将其更正in the future release。

与此同时，我根据their code编写了一个修补方法：

（这是必要的，因为（1）我们仍然需要等待正确的发布，（2）我们需要处理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
}

Android Bug？：String.substring（5）.replace（“”，“”）//空字符串

1 个答案:

宾果！我找到了这个错误！

完整解决方法

Android Bug？ ：String.substring（5）.replace（“”，“”）//空字符串

1 个答案:

宾果！我找到了这个错误！

完整解决方法

Android Bug？：String.substring（5）.replace（“”，“”）//空字符串