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copied!<p>Just look at bytecode of two different usages (with local variable a and without it). As you may see that If only static a is defined compiler will directly use 30 <code>(3: bipush 30)</code> If local variable a is defined local variable 1 local1 is pushed then multiply operation is done. </p> <pre><code> 5: iload_1 6: iconst_2 7: imul </code></pre> <p>if you want to use both of them you have to Usage Class name where static variable is defined.</p> <pre><code>System.out.println(a*2); // will print 6 System.out.println(MyFace.a); //will print 15 </code></pre> <p><strong>Here is a the example code local variable a is defined</strong></p> <pre><code>public class XFace implements MyFace { @Override public void smile() { int a=3; System.out.println(a*2); // will print 6 } } Compiled from "XFace.java" public class XFace extends java.lang.Object implements MyFace{ public XFace(); Code: 0: aload_0 1: invokespecial #10; //Method java/lang/Object."<init>":()V 4: return public void smile(); Code: 0: iconst_3 1: istore_1 2: getstatic #17; //Field java/lang/System.out:Ljava/io/PrintStream; 5: iload_1 6: iconst_2 7: imul 8: invokevirtual #23; //Method java/io/PrintStream.println:(I)V 11: return } ********************************************* </code></pre> <p><strong>Here is a the example code static variable a is defined</strong></p> <pre><code>public class XFace implements MyFace { @Override public void smile() { //int a=3; System.out.println(a*2); // will print 30 } } Compiled from "XFace.java" public class XFace extends java.lang.Object implements MyFace{ public XFace(); Code: 0: aload_0 1: invokespecial #10; //Method java/lang/Object."<init>":()V 4: return public void smile(); Code: 0: getstatic #17; //Field java/lang/System.out:Ljava/io/PrintStream; 3: bipush 30 5: invokevirtual #23; //Method java/io/PrintStream.println:(I)V 8: return } </code></pre> <p>to print byte code from compiled class file use javap tool under $JDK_HOME/bin</p>

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