相关学习推荐：java基础教程
下面有段简单的代码
public class StringPlusTest{ public static void main(String[] args) { String s1 = "aaa"; String s2 = "bbb"; String s = "ccc" +s1 + s2 +"ddd"; }}使用 javap -c .\StringPlusTest.class反编译一下，得到
Compiled from "StringPlusTest.java"public class com.epoint.codetuning.test.StringPlusTest { public com.epoint.codetuning.test.StringPlusTest(); Code: 0: aload_0 1: invokespecial #1 // Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: ldc #2 // String aaa 2: astore_1 3: ldc #3 // String bbb 5: astore_2 6: new #4 // class java/lang/StringBuilder 9: dup 10: invokespecial #5 // Method java/lang/StringBuilder."<init>":()V 13: ldc #6 // String ccc 15: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 18: aload_1 19: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 22: aload_2 23: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 26: ldc #8 // String ddd 28: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 31: invokevirtual #9 // Method java/lang/StringBuilder.toString:()Ljava/lang/String; 34: astore_3 35: return}其中，
ldc 把常量池中的项压入栈astore_1 将引用类型或returnAddress类型值存入局部变量1astore_2 将引用类型或returnAddress类型值存入局部变量2new 创建一个新对象dup 复制栈顶部一个字长内容invokespecial 根据编译时类型来调用实例方法aload_1 从局部变量1中装载引用类型值aload_2 从局部变量2中装载引用类型值astore_3 将引用类型或returnAddress类型值存入局部变量3
