DeadException
Exception created but not thrown

Severity
ERROR
Has Fix?
REQUIRES_HUMAN_ATTENTION

Alternate names: ThrowableInstanceNeverThrown

The problem

The exception is created with new, but is not thrown, and the reference is lost.

Suppression

Suppress false positives by adding the suppression annotation @SuppressWarnings("DeadException") to the enclosing element.


Positive examples

DeadExceptionPositiveCases.java

/*
* Copyright 2011 The Error Prone Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/


package com.google.errorprone.bugpatterns.testdata;

public class DeadExceptionPositiveCases {
public void error() {
// BUG: Diagnostic contains: throw new RuntimeException
new RuntimeException("Not thrown, and reference lost");
}

public void fixIsToDeleteTheFirstStatement() {
// BUG: Diagnostic contains: remove this line
new IllegalArgumentException("why is this here?");
int i = 1;
System.out.println("i = " + i);

if (true) {
// BUG: Diagnostic contains: remove this line
new RuntimeException("oops");
System.out.println("another statement after exception");
}

switch (0) {
default:
// BUG: Diagnostic contains: remove this line
new RuntimeException("oops");
System.out.println("another statement after exception");
}
}

public void firstStatementWithNoSurroundingBlock() {
if (true)
// BUG: Diagnostic contains: throw new InterruptedException
new InterruptedException("this should be thrown");

if (true) return;
else
// BUG: Diagnostic contains: throw new ArithmeticException
new ArithmeticException("should also be thrown");

switch (4) {
case 4:
System.out.println("4");
break;
default:
// BUG: Diagnostic contains: throw new IllegalArgumentException
new IllegalArgumentException("should be thrown");
}
}

public void testLooksLikeAJunitTestMethod() {
// BUG: Diagnostic contains: throw new RuntimeException
new RuntimeException("Not thrown, and reference lost");
}

{
// BUG: Diagnostic contains: throw new Exception
new Exception();
}
}

Negative examples

DeadExceptionNegativeCases.java

/*
* Copyright 2011 The Error Prone Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/


package com.google.errorprone.bugpatterns.testdata;

public class DeadExceptionNegativeCases {
public void noError() {
Exception e = new RuntimeException("stored");
e = new UnsupportedOperationException("also stored");
throw new IllegalArgumentException("thrown");
}

public Exception returnsException() {
return new RuntimeException("returned");
}
}