53 @java.io.Serial
54 private static final long serialVersionUID = 5162710183389028792L;
55
56 /**
57 * Constructs a {@code NullPointerException} with no detail message.
58 */
59 public NullPointerException() {
60 super();
61 }
62
63 /**
64 * Constructs a {@code NullPointerException} with the specified
65 * detail message.
66 *
67 * @param s the detail message.
68 */
69 public NullPointerException(String s) {
70 super(s);
71 }
72
73 /**
74 * Returns the detail message string of this throwable.
75 *
76 * <p> If a non-null message was supplied in a constructor it is
77 * returned. Otherwise, an implementation specific message or
78 * {@code null} is returned.
79 *
80 * @implNote
81 * If no explicit message was passed to the constructor, and as
82 * long as certain internal information is available, a verbose
83 * description of the null reference is returned.
84 * The internal information is not available in deserialized
85 * NullPointerExceptions.
86 *
87 * @return the detail message string, which may be {@code null}.
88 */
89 public String getMessage() {
90 String message = super.getMessage();
91 if (message == null) {
92 return getExtendedNPEMessage();
93 }
94 return message;
95 }
96
97 /**
98 * Get an extended exception message. This returns a string describing
99 * the location and cause of the exception. It returns null for
100 * exceptions where this is not applicable.
101 */
102 private native String getExtendedNPEMessage();
103 }
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53 @java.io.Serial
54 private static final long serialVersionUID = 5162710183389028792L;
55
56 /**
57 * Constructs a {@code NullPointerException} with no detail message.
58 */
59 public NullPointerException() {
60 super();
61 }
62
63 /**
64 * Constructs a {@code NullPointerException} with the specified
65 * detail message.
66 *
67 * @param s the detail message.
68 */
69 public NullPointerException(String s) {
70 super(s);
71 }
72
73 private static final String mustComputeExtendedNPEMessage = "1";
74 private static final String noExtendedNPEMessage = "2";
75 private volatile transient String extendedMessage;
76
77 /**
78 * {@inheritDoc}
79 */
80 public synchronized Throwable fillInStackTrace() {
81 // After the stack trace is changed the extended NPE algorithm
82 // will compute a wrong message. So compute it beforehand.
83 if (extendedMessage == null) {
84 // The first call. Don't compute the message, we'll
85 // do it lazily.
86 extendedMessage = mustComputeExtendedNPEMessage;
87 } else if (extendedMessage == mustComputeExtendedNPEMessage) {
88 // The second call.
89 extendedMessage = getExtendedNPEMessage();
90 }
91 return super.fillInStackTrace();
92 }
93
94 /**
95 * Returns the detail message string of this throwable.
96 *
97 * <p> If a non-null message was supplied in a constructor it is
98 * returned. Otherwise, an implementation specific message or
99 * {@code null} is returned.
100 *
101 * @implNote
102 * If no explicit message was passed to the constructor, and as
103 * long as certain internal information is available, a verbose
104 * description of the null reference is returned.
105 * The internal information is not available in deserialized
106 * NullPointerExceptions.
107 *
108 * @return the detail message string, which may be {@code null}.
109 */
110 public String getMessage() {
111 String message = super.getMessage();
112 if (message == null) {
113 synchronized(this) {
114 if (extendedMessage == mustComputeExtendedNPEMessage) {
115 // Only the original stack trace was filled in. Message will
116 // compute correctly.
117 extendedMessage = getExtendedNPEMessage();
118 }
119 if (extendedMessage != noExtendedNPEMessage) {
120 return extendedMessage;
121 }
122 }
123 }
124 return message;
125 }
126
127 /**
128 * Get an extended exception message. This returns a string describing
129 * the location and cause of the exception. It returns noExtendedNPEMessage for
130 * exceptions where this is not applicable.
131 */
132 private String getExtendedNPEMessage() {
133 String msg = getExtendedNPEMessage0();
134 if (msg == null) return noExtendedNPEMessage;
135 return msg;
136 }
137
138 private native String getExtendedNPEMessage0();
139 }
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