Nullpointerexception when trying to obtain Java compiler instance

Question

Next, I’m trying to get an instance of the Java compiler, using the following code:

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

if (compiler == null) {
    System.out.println("No compiler");
    return;
}

The problem is that it always falls inside the if, and I can’t understand why.

I want to know what I’m doing wrong.

Answer 1

This problem occurs when you run the code with a JRE and not a JDK. To solve, you need to inform the JDK path in the property java.home. One way to do this programmatically is to directly inform the value of the property in the system:

System.setProperty("java.home", "caminho_do_java");
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

if (compiler == null) {
    System.out.println("No compiler");
    return;
}

Replace the string caminho_do_java by the way of your JDK.