The Java Tutorials have been written for JDK 8.Java教程是为JDK 8编写的。Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.本页中描述的示例和实践没有利用后续版本中引入的改进，并且可能使用不再可用的技术。See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.有关Java SE 9及其后续版本中更新的语言特性的摘要，请参阅Java语言更改。
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.有关所有JDK版本的新功能、增强功能以及已删除或不推荐的选项的信息，请参阅JDK发行说明。
There a several modifiers that may be part of a method declaration:
public, protected, and privatestaticfinalabstractsynchronizednativestrictfpThe MethodModifierSpy
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import static java.lang.System.out;
public class MethodModifierSpy {
private static int count;
private static synchronized void inc() { count++; }
private static synchronized int cnt() { return count; }
public static void main(String... args) {
try {
Class<?> c = Class.forName(args[0]);
Method[] allMethods = c.getDeclaredMethods();
for (Method m : allMethods) {
if (!m.getName().equals(args[1])) {
continue;
}
out.format("%s%n", m.toGenericString());
out.format(" Modifiers: %s%n",
Modifier.toString(m.getModifiers()));
out.format(" [ synthetic=%-5b var_args=%-5b bridge=%-5b ]%n",
m.isSynthetic(), m.isVarArgs(), m.isBridge());
inc();
}
out.format("%d matching overload%s found%n", cnt(),
(cnt() == 1 ? "" : "s"));
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
}A few examples of the output MethodModifierSpy
$ java MethodModifierSpy java.lang.Object wait public final void java.lang.Object.wait() throws java.lang.InterruptedException Modifiers: public final [ synthetic=false var_args=false bridge=false ] public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException Modifiers: public final [ synthetic=false var_args=false bridge=false ] public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException Modifiers: public final native [ synthetic=false var_args=false bridge=false ] 3 matching overloads found
$ java MethodModifierSpy java.lang.StrictMath toRadians public static double java.lang.StrictMath.toRadians(double) Modifiers: public static strictfp [ synthetic=false var_args=false bridge=false ] 1 matching overload found
$ java MethodModifierSpy MethodModifierSpy inc private synchronized void MethodModifierSpy.inc() Modifiers: private synchronized [ synthetic=false var_args=false bridge=false ] 1 matching overload found
$ java MethodModifierSpy java.lang.Class getConstructor public java.lang.reflect.Constructor<T> java.lang.Class.getConstructor (java.lang.Class<T>[]) throws java.lang.NoSuchMethodException, java.lang.SecurityException Modifiers: public transient [ synthetic=false var_args=true bridge=false ] 1 matching overload found
$ java MethodModifierSpy java.lang.String compareTo public int java.lang.String.compareTo(java.lang.String) Modifiers: public [ synthetic=false var_args=false bridge=false ] public int java.lang.String.compareTo(java.lang.Object) Modifiers: public volatile [ synthetic=true var_args=false bridge=true ] 2 matching overloads found
Note that Method.isVarArgs() returns true for Class.getConstructor(). This indicates that the method declaration looks like this:
public Constructor<T> getConstructor(Class<?>... parameterTypes)
not like this:
public Constructor<T> getConstructor(Class<?> [] parameterTypes)
Notice that the output for String.compareTo() contains two methods. The method declared in String.java:
public int compareTo(String anotherString);
and a second synthetic or compiler-generated bridge method. This occurs because String implements the parameterized interface Comparable. During type erasure, the argument type of the inherited method Comparable.compareTo() is changed from java.lang.Object to java.lang.String. Since the parameter types for the compareTo methods in Comparable and String no longer match after erasure, overriding can not occur. In all other circumstances, this would produce a compile-time error because the interface is not implemented. The addition of the bridge method avoids this problem.
Method implements java.lang.reflect.AnnotatedElement. Thus any runtime annotations with java.lang.annotation.RetentionPolicy.RUNTIME may be retrieved. For an example of obtaining annotations see the section Examining Class Modifiers and Types.