java中 boolean类型占多少字节
今天面试问到了这个问题,java中boolean类型到底占多少字节呢,到网上搜了下,最后采用了这个答案:
答:我的结论是:
1)boolean a=true;//这个a在JVM中占4个字节即:32位。
2)boolean[] b = new boolean[10];//数组时,每一个boolean在JVM中占一个字节。
理由:
1)JAVA规范中没有定义boolean类型的大小。
2)但是:在JVM规范第2版中讲得十分清楚。我上边的结论就是从它当中取出来的。
根据:(JVM规范第2版 3.3.4节)
Instead, expressions in the Java programming language that operate on boolean values are compiled to use values of the Java virtual machine int data type.
Where Java programming language boolean values are mapped by compilers to values of Java virtual machine type int, the compilers must use the same encoding. 而:Java virtual machine type int, whose values are 32-bit signed two's-complement integers。
Arrays of type boolean are accessed and modified using the byte array instructions
In Sun's JDK releases 1.0 and 1.1, and the Java 2 SDK, Standard Edition, v1.2, boolean arrays in the Java programming language are encoded as Java virtual machine byte arrays, using 8 bits per boolean element.
今天面试问到了这个问题,java中boolean类型到底占多少字节呢,到网上搜了下,最后采用了这个答案:
答:我的结论是:
1)boolean a=true;//这个a在JVM中占4个字节即:32位。
2)boolean[] b = new boolean[10];//数组时,每一个boolean在JVM中占一个字节。
理由:
1)JAVA规范中没有定义boolean类型的大小。
2)但是:在JVM规范第2版中讲得十分清楚。我上边的结论就是从它当中取出来的。
根据:(JVM规范第2版 3.3.4节)
Instead, expressions in the Java programming language that operate on boolean values are compiled to use values of the Java virtual machine int data type.
Where Java programming language boolean values are mapped by compilers to values of Java virtual machine type int, the compilers must use the same encoding. 而:Java virtual machine type int, whose values are 32-bit signed two's-complement integers。
Arrays of type boolean are accessed and modified using the byte array instructions
In Sun's JDK releases 1.0 and 1.1, and the Java 2 SDK, Standard Edition, v1.2, boolean arrays in the Java programming language are encoded as Java virtual machine byte arrays, using 8 bits per boolean element.
本文探讨了Java中boolean类型的具体内存占用情况。通过分析JVM规范了解到,boolean变量在不同上下文中占用的字节数有所不同。对于单一的boolean变量,其在JVM中占用4个字节;而在boolean数组中,则每个元素占用1个字节。
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