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Add ClassSource.empty, ClassSource.attemptLoadFrom will also not

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tolerate nulls
This commit is contained in:
Glen Husman 2014-05-17 12:23:59 -07:00
parent 95087a5b9f
commit 0f5be7f1f1
1 changed files with 19 additions and 4 deletions
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23
ProtocolLib/src/main/java/com/comphenix/protocol/utility/ClassSource.java
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@ -1,5 +1,6 @@
package com.comphenix.protocol.utility;
import java.util.Collections;
import java.util.Map;
/**
@ -58,17 +59,31 @@ public abstract class ClassSource {
};
}
/**
* @return A ClassLoader which will never successfully load a class.
*/
public static ClassSource empty(){
return fromMap(Collections.<String, Class<?>>emptyMap());
}
/**
* Retrieve a class source that will attempt lookups in each of the given sources in the order they are in the array, and return the first value that is found.
* If the sources array is empty, null, or composed of all null elements, the returned ClassSource will be null. Null elements in the array are ignored.
* If the sources array is null or composed of any null elements, an exception will be thrown.
* @param sources - the class sources.
* @return A new class source.
*/
public static ClassSource attemptLoadFrom(final ClassSource... sources) {
ClassSource source = sources != null && sources.length >= 1 ? sources[0] : null;
if(sources.length == 0){ // Throws NPE if sources is null, which is what we want
return ClassSource.empty();
}
ClassSource source = sources[0];
for(int i = 1; i < sources.length; i++){
source = sources[i] == null ? source :
source == null ? sources[i] : source.retry(sources[i]);
if(source == null || sources[i] == null){
throw new IllegalArgumentException("Null values are not permitted as ClassSources.");
}
source = source.retry(sources[i]);
}
return source;
}